Plain meaning
Start with the shortest useful explanation before going deeper.
An on-chain account defining a token type. A mint specifies: supply (total minted), decimals (0 for NFTs, 6 for USDC, 9 for most tokens), mint authority (who can mint), and optional freeze authority. Each unique token (USDC, JitoSOL, etc.) has exactly one mint account. Mint address serves as the token's unique identifier.