Smart Contract
Self-executing code on the blockchain that runs when conditions are met.
A smart contract is a program that lives on the blockchain and automatically executes when predefined conditions are met — without intermediaries, judges, or banks.
Example: "If user A sends 1 ETH before date X, send them 1000 tokens." The code does this automatically, impartially, and immutably.
Ethereum popularized smart contracts and today a huge ecosystem of DeFi protocols, NFT markets, games, and DAOs uses them.
Risks: code bugs are permanent and can lead to loss of funds (famous example: The DAO hack in 2016).