Glossary
List of key terms related to the Celo platform, networks, tools, and blockchain technology.
Account
Identifies an account on Celo. There are two types of account. Externally owned accounts have an associated CELO balance and are controlled by a user holding the associated public-private keypair. Contract accounts contain the code and data of a single smart contract which can be called and manipulate its own stored data.
Address
A unique identifier for an account on any blockchain.
Alfajores
The first public Celo test network, available for developers to use freely subject to the Alfajores Testnet Disclaimer.
Attestation
Generally, support for an entity having an associated identity. In Celo, each attestation confirms that an account has access to a message sent to a specific identifier typically a mobile phone number via an Attestation Provider via Celo's ODIS.
Attestation Service
Former name for what has become Social Connect.
Baklava
The second public Celo test network, intended for use as a testing ground for protocol changes and node operator configurations. It is subject to the Baklava Testnet Disclaimer.
Batcher
A component in the OP-Stack architecture responsible for collecting Layer 2 transactions and submitting them to the Layer 1 in batches. The batcher helps optimize costs and efficiency by grouping multiple transactions together.
Block
The unit of update to the blockchain. A block consists of a header identifying its position in the chain and other metadata, and a body that contains a list of transactions, and data structures that describe the new state after executing those transactions.
Blockchain
A blockchain or cryptographic network is a broad term used to describe a database maintained by a distributed set of computers that do not share a trust relationship or common ownership. This arrangement is referred to as decentralized. The content of a blockchain's database, or ledger, is authenticated using cryptographic techniques, preventing its contents being added to, edited or removed except according to a protocol operated by the network as a whole.
Bridge
A protocol or system that enables the transfer of assets and data between different blockchains. Celo supports both native bridging to Ethereum and third-party bridges to other networks.
Byzantine Fault Tolerant (BFT) Consensus
A form of consensus algorithm in which up to a third of participants can be faulty or malicious.
Carbon Offsetting Fund
An account that receives a transfer as part of epoch rewards to cover the cost of offsetting the carbon generated by the hardware footprint required to operate the Celo network. The account that receives these funds and the amount is determined from time to time by on-chain governance proposal.
CELO
The ticker symbol for the Celo native asset, often written in capital letters to avoid confusion with references to the Celo protocol.
Celo
An open platform that makes financial tools accessible to anyone with a mobile phone.
Celo Foundation
A mission-driven foundation responsible for education, community engagement, and ecosystem support of the Celo platform.
Celo Gold
The deprecated name for the Celo native asset, which now is referred to simply as "Celo" or preferably "CELO".
Celo Native Asset
The Celo native asset which may be used to take actions on-chain, such as participating in Governance.
cLabs, Celo Labs
The team that is a core contributor to shape the Celo protocol with the input of the larger Celo Community.
Claim
Part of the metadata that Celo can associate with an address, a claim is used by an account to assert it has control over a particular off-chain entity (for example, a DNS domain name, an account on a third party service, etc). Claims can only be verified off-chain.
Client
See Node.
Community Fund
An account that supports the development and operational costs of the Celo protocol. The Community Fund is maintained by a transfer made as part of Epoch Rewards, and is intended to cover costs beyond the other specific incentives provided to community RPC nodes and groups. Awards can be made through an on-chain governance proposal.
Community RPC node
A node service that runs an RPC endpoint for the Celo network, allowing users and applications to access blockchain data and submit transactions. These nodes help decentralize infrastructure and require Locked CELO as stake for registration.
Consensus
An algorithm that enables multiple computers to reach a decision on a single value proposed by one of them, despite network or computer failures.
ContractKit
A library to help developers and operators of nodes to interact with the Celo Blockchain and Celo Core Contracts. For dApp developers we suggest using viem or wagmi.
Cryptocurrency
Celo has a native unit of accounting, the cryptocurrency CELO, comparable to Ether on Ethereum. CELO has token duality, meaning it can be used as a native token and an ERC20 token. Celo's ledger consists of accounts, identified by an address. There are two types of accounts. Externally owned accounts have an associated CELO balance and are controlled by a user holding the associated public-private keypair. Contract accounts contain the code and data of a single smart contract which can be called and manipulate its own stored data.
DApp
Short for Decentralized Application. An application, usually a mobile application, which to deliver its functionality connects to a decentralized network like Celo, rather than to centralized services in a single organization's data centers.
Dango
Celo's first Layer 2 public testnet that launched in July 2024. Dango allowed developers and infrastructure providers to familiarize themselves with the L2 environment before the mainnet migration. The testnet was shut down in October 2024 after serving its purpose as a testing ground for the L2 transition.
DeFi
Decentralized Finance; open source software and networks without intermediaries in the financial space.
Derivation Path
A derivation path defines how private keys and addresses are derived from a mnemonic. The Bitcoin community defined the standards for derivation paths in BIP39 and BIP42 and BIP44. A registry of coins/chains and their paths is maintained and includes Celo and Ethereum paths.
Eclair
A specialized Celo testnet designed to showcase the integration of EigenDA v2 and Succinct Lite. Eclair serves as a testing environment for advanced data availability solutions and zero-knowledge proof systems, allowing developers to experiment with cutting-edge infrastructure before deployment to mainnet.
EigenDA
A high-throughput, decentralized data availability (DA) service built on EigenLayer that Celo uses for publishing transaction data. EigenDA provides scalable and secure data availability for Layer 2 networks like Celo.
EOA or externally owned account
Ethereum term to designate addresses operated by users, as opposed to contract addresses.
Epoch
Since the Celo migration to L2, an epoch is a variable number of blocks set to be at least as long as a day's time. Epoch changes are triggered through a permissionless smart contract call.
When Celo was an L1 blockchain, an epoch was a fixed number of blocks, configured in the network's genesis block, during which the same validator set was used for consensus. A validator election was carried out after the last block of an epoch, and any resulting changes to the validator set were written into that block's header.
For more details on the changes between L1 and L2, refer to the specs.
Epoch Rewards
Funds disbursed by the protocol at the end of every epoch as incentives for community RPC node providers, holders of Locked CELO that participated in elections, the Reserve, the Community Fund, and the Carbon Offsetting Fund.
ERC-20
A standard interface for implementing tokens as smart contracts. Balances associated with addresses are typically maintained inside the contract's storage. Both CELO, Celo Dollars and other Celo stablecoins implement the ERC-20 interface.
EVM
The Ethereum Virtual Machine. A runtime environment used by smart contracts on Ethereum and Celo.
Externally Owned Account (EOA)
An account owned by a private key which has full control to send transactions from the account by signing and submitting the transaction to the blockchain. All transaction on Celo must originate from an EOA, which pays for the transaction fees.
Fee Abstraction
A unique feature of Celo that allows users to pay transaction fees in various ERC-20 tokens, not just the native CELO token. This enables users to transact without needing to hold CELO for gas, making the platform more accessible.
Finality
The state when a transaction or block is considered permanently settled and cannot be reversed. On Celo L2, finality depends on the sequencer, batcher, proposer, and ultimately on Ethereum's finality.
Forno
Celo's hosted node service that provides JSON-RPC endpoints on a best-effort basis for developers to connect to the Celo network without running their own node infrastructure.
Full Node
A computer running the Celo Blockchain software that maintains a full copy of the blockchain locally.
Gas
A step of execution of a smart contract. Different operations consume different amounts of gas. To prevent denial-of-service attacks, transactions specify a maximum gas which bounds the steps of execution before a transaction is reverted.
Gas Price
Determines the unit price for gas, i.e. cost for a transaction to perform one step of execution. This is used to prioritize which transactions the network applies.
Gas Price Minimum
The minimum unit price for gas that the Celo protocol will accept. This value changes from block to block in response to congestion, increasing as more transactions are competing for the limited capacity of the network. A transaction specifying a gas price below the Gas Price Minimum will not be processed until the Gas Price Minimum falls.
Genesis block
The very first block in the blockchain, provided as configuration to Celo Blockchain nodes.
Governable
A smart contract that is owned by the Celo Governance mechanism and so can be changed or updated by an on-chain governance proposal.
Governance
A part of Celo that allow the protocol to be upgraded, and other actions to be taken on behalf of the network, by holding a referendum process in which CELO holders vote for proposals submitted by the community.
Group Share
The proportion of epoch rewards for an elected community RPC node that is passed to the group that caused it to be elected. This is a property that can be configured by each group.
Header
See Block.
HSM
Hardware Security Module. A hardware device that hosts one or more private keys and signs data without passing the key off the device.
Key Rotation
The creation of a new cryptographic key to replace an existing key in active use.
Layer 1 (L1)
Refers the Ethereum blockchain, used in contrast to layer 2, which refers to Celo.
Layer 2 (L2)
Refers to the Celo blockchain and is used in contrast to layer 1, which refers to the Ethereum blockchain.
Locked CELO
CELO balances held in escrow at the LockedGold contract for the account that deposited it there. This permits that balance to be used for voting in elections, governance proposals, and to meet staking requirements for registering a community RPC node.
Locked Gold
Locked Gold is the old name for Locked CELO.
Mainnet
The Celo production network.
Mento
The decentralized stability protocol that maintains Celo's family of stablecoins. Mento uses algorithmic monetary policy and over-collateralization to ensure price stability.
Originally part of the Celo protocol, Mento has evolved into its own independent protocol.
MiniPay
A mobile wallet and payments app by Opera built on Celo, designed to make cryptocurrency and DeFi accessible to users through a simple, user-friendly interface. MiniPay supports features like peer-to-peer payments and DApp integration.
Node
A running instance of the Celo Blockchain software. Used interchangeably with 'Client'.
On-chain
An interaction that takes place solely through a transaction being executed on the blockchain and updating the state of the ledger.
OP-Stack
A modular blockchain development framework created by Optimism that serves as the foundation for Celo's Layer 2 implementation. The OP-Stack provides standardized components for building Ethereum Layer 2 networks.
Optimism
The Ethereum Layer 2 network that developed the OP-Stack framework. Celo's L2 is built using Optimism's proven infrastructure and shares revenue with the OP-Stack ecosystem.
Oracle
External data sources that provide real-world information to smart contracts on the blockchain. Oracles enable smart contracts to access off-chain data such as price feeds, weather data, or other external information needed for decentralized applications and protocols like Mento.
Proposer
A component in the OP-Stack architecture responsible for submitting Layer 2 state commitments to the Layer 1. The proposer ensures that L2 transactions are properly recorded and finalized on L1.
Proof-of-Stake
When Celo was an L1, the system that determined the participants in a Byzantine Fault Tolerant consensus mechanism. Celo's Proof-of-Stake mechanism permitted accounts to convert units of CELO into Locked CELO then vote for Validator Groups, such that an election held at the end of every epoch selected a new set of validators for the following epoch.
RC1
RC1, which stands for Release Candidate 1, was the first network that had the potential to become the Celo Mainnet. It was promoted to Mainnet after the Celo community voted to enable CELO transfers on the network on May 18, 2020.
Savings Circle
A common practice in societies without easy access to banking (source); a peer-to-peer savings and loan group.
Slashing
The reduction in the stake of a community RPC node and group for a particular action not conducive to the health of the network.
Smart Contracts
Programs that are deployed to a blockchain and execute on its nodes. They operate on data on the blockchain, and on external inputs received in transactions or messages to the blockchain, and may update the state of the blockchain, including account balances. On Celo and Ethereum, smart contracts are written in languages like Solidity that produce bytecode for the Ethereum Virtual Machine or EVM, a runtime environment.
Solidity
The preferred language for writing Smart Contracts on the Celo platform.
Stablecoin
A stablecoin is a type of cryptocurrency whose price tracks an external currency or commodity.
Stake
Locked CELO that a community RPC provider puts at risk at the point of registration. A portion of a stake can be slashed for particular actions not conducive to the health of the network.
Sequencer
A component in the OP-Stack architecture responsible for ordering and executing Layer 2 transactions. The sequencer processes transactions in real-time and provides fast transaction confirmation before they are batch-submitted to the Layer 1.
Self
A decentralized identity protocol that enables users to manage their digital identity across applications and services. Self provides privacy-preserving identity verification. Learn more at self.xyz.
Social Connect
Celo's decentralized identity protocol that enables users to connect their phone numbers and other identifiers to their blockchain addresses while preserving privacy.
Formerly known as the Attestation Service and now a part of Self.
Testnet
A test network. Its tokens hold no real world economic value.
Transaction
Requests to make a change to the state of the blockchain. They can: transfer value between accounts; execute a function in a smart contract and pass in arguments (perhaps causing other smart contracts to be called, update their storage, or transfer value); or create a new smart contract.
Transaction Fees
To avoid Denial-of-Service attacks and ensure termination of calls to smart contract code, the account sending a transaction pays transaction fees for its execution steps using its own balance. Transactions specify a maximum gas which bounds the steps of execution before a transaction is reverted. A gas price determines the unit price for each step, and is used to prioritize which transactions the network applies. In Celo, transaction fees can be paid in ERC-20 currencies and gas pricing works differently from Ethereum.
Token Duality
A unique feature of CELO that allows it to function both as the native gas token for the Celo network and as an ERC-20 token that can be transferred and used in smart contracts.
Unlocking Period
The elapsed time between an account requesting an amount of Locked CELO be unlocked and the first point it can be withdrawn.
Valora
Celo's flagship mobile wallet application that provides easy access to DeFi, payments, and cryptocurrency management. Valora offers features like peer-to-peer payments, savings, and DApp integration, making Web3 accessible through a user-friendly mobile interface.
Validator
When Celo was an L1, validator referred both to the entity in the proof-of-stake mechanism that could be associated with a validator group and subsequently elected; and a running instance of the Celo Blockchain software that was configured and ready (if elected) to participate in the Byzantine Fault Tolerant consensus algorithm to agree on new blocks to append to the blockchain ledger.
For historical reasons, the term validator is still present in the codebase and documentation, but it is now used to refer to community RPC nodes.
Validator Group
When Celo was an L1, the entity in the proof-of-stake mechanism that could associate validators, receive votes from holders of Locked CELO and cause those validators to be elected.
For historical reasons, the term validator group is still present in the codebase and documentation, but it is now used to refer to community RPC nodes.
Validator Set
When Celo was an L1, the set of elected validators (with respect to a specific epoch) that participated in consensus.
Wallet
A DApp that allows a user to manage an account, and usually stores the associated private key.