#[derive(Accounts)] (Anchor)

The Anchor macro that defines the accounts struct for an instruction. Each field specifies an account with validation constraints. Account types include: `Account<'info, T>` (deserialized), `Signer<'info>` (must sign), `Program<'info, T>` (program reference), `SystemAccount<'info>`, and `UncheckedAccount<'info>` (no validation, use carefully).