Reference
Blockchain glossary
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Fundamentals
10 terms- Blockchain
- An append-only ledger of transactions grouped into blocks, each cryptographically linked to the one before it and replicated across many independent computers. #blockchain
- Block
- A batch of transactions bundled together with a timestamp and a reference (hash) to the previous block. #block
- Hash
- A fixed-length fingerprint produced by a one-way function. The same input always yields the same hash; the smallest change produces a completely different one. #hash
- Node
- A computer running the blockchain's software that stores a copy of the ledger and helps validate and relay transactions. #node
- Consensus
- The process by which distributed nodes agree on which transactions are valid and what the current state of the ledger is. #consensus
- Proof of Work
- A consensus mechanism where miners spend computing power to find a valid hash, securing the chain by making attacks expensive. #pow
- Proof of Stake
- A consensus mechanism where validators lock up (stake) tokens for the right to propose and attest blocks, and can lose the stake for misbehaving. #pos
- Immutable
- Designed to resist changes after confirmation. How final a record is depends on the network, its consensus rules, and how much confirmation has accumulated. #immutable
- Decentralized
- Operated by many independent participants rather than a single authority, so no one party can unilaterally control it. #decentralized
- 51% attack
- An attack where a single party controls a majority of the network's mining or staking power and can rewrite recent history. #51-attack
Layer 1, Layer 2 & Rollups
17 terms- Layer 1
- A base blockchain, such as Bitcoin or Ethereum, with its own consensus and security model. Some scaling systems settle to a Layer 1, while independent sidechains do not. #layer-1
- Layer 2
- A scaling system that executes transactions outside a base chain and uses that chain for some security or settlement guarantees. The strength of those guarantees depends on the specific design and available data. #layer-2
- Rollup
- A scaling design that executes transactions outside Layer 1 and posts transaction data or commitments to it. Optimistic rollups use challenge mechanisms; validity rollups use cryptographic proofs. Their guarantees depend on the implementation and data availability. #rollup
- Optimistic rollup
- A rollup whose proposed state transitions can be challenged during a dispute window. Security depends on an effective challenge mechanism and the availability of transaction data. #optimistic-rollup
- ZK-rollup
- A rollup that uses cryptographic validity proofs to establish correct state transitions. Proof verification does not by itself guarantee censorship resistance, withdrawal speed or data availability. #zk-rollup
- Fraud proof
- Evidence submitted during an optimistic rollup's challenge window showing a posted batch was invalid, which reverts it and penalizes the poster. #fraud-proof
- Validity proof
- A cryptographic proof (e.g. a zk-SNARK) that mathematically demonstrates a batch of transactions was executed correctly, without re-running them. #validity-proof
- Sequencer
- The party - often centralized, at least initially - that orders and batches transactions on a Layer 2 before posting them to Layer 1. #sequencer
- Data availability
- The guarantee that the underlying transaction data behind a block or batch is actually published, so anyone can verify or reconstruct the chain's state. #data-availability
- Finality
- The point at which a transaction is considered irreversible. L2 transactions often have quick 'soft' finality but only reach 'hard' finality once settled on L1. #finality
- Blockchain trilemma
- The observation that decentralization, security, and scalability are hard to maximize simultaneously - improving one tends to pressure the others. #trilemma
- Sidechain
- An independent blockchain connected to a main chain via a bridge, with its own consensus and security - meaning it does not inherit the main chain's security. #sidechain
- Bridge
- A mechanism for coordinating assets or messages across networks. Depending on its design, it may lock and mint, burn and release, or exchange assets through liquidity providers. #bridge
- State channel
- A scaling technique where participants transact off-chain directly with each other and only settle the final outcome on-chain. #state-channel
- TPS
- Transactions per second - a common (if imperfect) measure of a blockchain's throughput capacity. #tps
- Calldata
- A field for transaction input data on Ethereum. Rollups can also publish data in lower-cost blobs introduced by EIP-4844; the data-publication method affects their fees. #calldata
Wallets & Keys
5 terms- Wallet
- Software (or hardware) that stores your private keys and lets you sign transactions. The wallet holds keys, not coins - the coins live on-chain. #wallet
- Private key
- A secret number that controls an account. Anyone with it can move the funds, so it must never be shared. #private-key
- Public key
- A value derived from the private key that others use to verify your signatures. Your address is usually derived from it. #public-key
- Seed phrase
- A human-readable list of 12–24 words that can regenerate all the private keys in a wallet. Whoever holds it controls the wallet. #seed-phrase
- Cold storage
- Keeping private keys fully offline (e.g. on a hardware wallet or paper) so they can't be reached by online attackers. #cold-storage
DeFi & Tokens
10 terms- Gas
- The fee paid to have the network process a transaction or run a smart contract. Priced in the chain's native token. #gas
- Smart contract
- A program deployed on-chain that runs exactly as written when called, without a middleman. The basis of DeFi, NFTs, and most dApps. #smart-contract
- DeFi
- Decentralized Finance - financial services (lending, trading, saving) built from smart contracts instead of banks or brokers. #defi
- DEX
- A decentralized exchange that lets users swap tokens peer-to-contract, often using an automated market maker instead of an order book. #dex
- AMM
- Automated Market Maker - a smart contract that prices swaps from a pool of two assets using a formula rather than matching buyers and sellers. #amm
- Liquidity
- Assets deposited into a pool or market so that others can trade against them. Providers earn a share of the fees. #liquidity
- Stablecoin
- A token designed to hold a steady value, usually pegged to a currency like the US dollar, via reserves or algorithms. #stablecoin
- Token
- A unit of value issued on top of a blockchain via a smart contract, following a standard like ERC-20 (fungible) or ERC-721 (non-fungible). #token
NFTs & Ownership
1 terms- NFT
- Non-Fungible Token - a unique on-chain token used to represent ownership of a specific item such as art, collectibles, or access passes. #nft
Security & Safety
1 terms- Rug pull
- A scam where a project's creators drain the liquidity or funds and disappear, leaving holders with worthless tokens. #rug-pull
Primary references
Documentation and standards
References added
Official technical references for further verification. A source link is not a guarantee that every earlier editorial sentence has been reverified; provider specifications may also change over time.
Definitions simplify some protocol-specific details; consult the specifications for exact network rules.
- Solana RPC HTTP referenceSolanaRead source ↗
- Optimistic rollupsethereum.orgRead source ↗
- EIP-4844 blob transactionsEthereum Improvement ProposalsRead source ↗
- ERC-20 token and allowance specificationEthereum Improvement ProposalsRead source ↗
- Uniswap v3 swap mechanicsUniswapRead source ↗
- ERC-721 non-fungible token standardEthereum Improvement ProposalsRead source ↗
- NFT metadata standardsOpenSeaRead source ↗