A smart contract is a self-executing program that carries out predefined actions on a blockchain without requiring a middleman or central authority.
The concept, proposed by Nick Szabo in the 1990s, was made practical with the launch of Ethereum in 2015, providing a platform for fully featured smart contracts.
Unlike its name suggests, a smart contract is not artificial intelligence and is not a legal contract in the traditional sense. It's simply code that says 'if this happens, then do that' and runs on a network that no single party controls.