A smart contract is a self-executing computer program that automatically enforces the terms of an agreement between parties. It is a piece of code that runs on a blockchain network and can facilitate, verify, and enforce the negotiation or performance of a contract without the need for intermediaries or third-party enforcement.

Smart contracts operate on the principle of if/then logic, where they automatically execute the terms of a contract once certain pre-defined conditions are met. They are transparent, immutable, and secure, and can be used for a wide range of applications such as financial transactions, supply chain management, and digital identity verification.

Smart contracts were first introduced in 1994 by Nick Szabo, a computer scientist and cryptographer, and gained widespread attention with the advent of blockchain technology. Ethereum, a decentralized blockchain platform, is one of the most popular platforms for creating and deploying smart contracts.