Canister

Internet Computer's core smart contract primitive: a WebAssembly module plus persistent memory, running on a subnet of ICP nodes. Canisters can hold gigabytes of state directly, serve HTTP requests, and make outbound HTTP calls — combining compute, storage, and web serving in one primitive. Written in Motoko or Rust. Reverse gas: canisters pay for their own computation in 'cycles,' so users don't need crypto to interact.