A smart contract is a self-executing program stored on a blockchain that runs automatically when predefined conditions are met. It is written in languages like Solidity and executed by technologies such as the Ethereum Virtual Machine (EVM). When a user sends a transaction to the contract, the network's nodes validate and execute its logic without intermediaries.
Smart contracts are used across many blockchains,not only Ethereum,and power a wide range of decentralized applications, including finance, gaming, and digital identity. For example, in the Ethereum Name Service (ENS), a smart contract manages domain registration: when a user pays the required fee, the contract verifies the transaction and assigns the name on-chain.
Smart contracts offer transparency and immutability, but their security depends entirely on the code. Bugs or logic flaws can lead to irreversible loss of funds or access. Once deployed, they cannot be modified, so audits and peer reviews are essential. In case of failure, there is no official support; users must rely on DAO governance, community channels, or legal mechanisms depending on the blockchain’s structure.