A smart contract is a computer program, stored on the blockchain. Smart contracts allow trustless transactions to be executed without third parties - the smart contract enforces the rules of the transaction automatically. These transactions are trackable and irreversible.
Key features of smart contracts are:
Autonomous: Once a smart contract is initiated, it can act by itself without further participant involvement. Decentralized: No single party has control over the entirety of the contract, and it cannot be modified after deployment. Deterministic: Outcomes can be determined from the inputs and the contract code.