Glossary
ABI
Application Binary Interface — the schema describing a contract's functions and events, used by clients to encode calls and decode results.
The Solidity / EVM ABI specifies how function names, argument types, and event signatures are serialized into the bytes a transaction carries (and into the bytes a contract emits as logs). It is the contract's machine-readable interface description.
Clients (wallets, ethers, viem, web3.js) hold the ABI JSON, encode calls into hex calldata, and decode return values and event topics back into typed values. Without the ABI, on-chain bytes are opaque — which is why block explorers ask you to upload the ABI before they can show "decoded" transactions.