Rent
Plain English
A small fee required to keep data stored on Solana. Accounts must hold minimum SOL balance to stay "rent-exempt" - basically a deposit that you get back when you close the account. Prevents blockchain bloat by making people pay for permanent storage.
Technical
Economic mechanism preventing state bloat by charging for account storage. Accounts below rent-exempt threshold pay recurring lamports until depleted, then get purged. Rent-exempt balance: (account size bytes) × rent rate. Most accounts maintain rent-exempt status. When accounts close, rent-exempt balance returns to owner. Implemented via System Program rent calculations.