Rent on Solana is a refundable SOL deposit that an account must hold to keep its data stored on the network. Rent is not a recurring charge, though. If you hold enough SOL and the account is rent-exempt indefinitely, closing the account returns your rent. Solflare suggests keeping roughly 0.005-0.05 SOL in reserve to cover rent and fees. Get the Solflare wallet or learn more about Solana.