Smart Contract
Plain English
Like a vending machine - you put in money, select what you want, and automatically get your item. Smart contracts are programs that automatically execute agreements when conditions are met, without needing a middleman. For example, automatically paying rent on the first of each month.
Technical
Self-executing code deployed on a blockchain that automatically enforces and executes the terms of an agreement when predetermined conditions are met. On Solana, these are called Programs and are compiled to BPF bytecode, storing state in separate Account data structures following the runtime’s architecture.