Mint authority is the power to create new units of a token. On networks with program-level token standards, that power is a specific on-chain permission that can be held by a key, a multisig, or a governance program - and on well-designed tokens, it is renounced or constrained once issuance is complete.
For a pegged or backed token, controlled minting against new reserves is the mechanism that keeps supply honest; for a fixed-supply token, an unrenounced mint authority is a standing risk that supply is not actually fixed.
Mint facts are stated per asset on U.CASH pages: who can mint, whether the authority is renounced or multisig-gated, and what the program's disclosure says. The diligence block puts them with freeze authority so the supply picture is one glance.
Every term behind the rails, the assets, and the settlement.