Federal permission to haul regulated freight for hire across state lines.
Granted by the FMCSA and tied to insurance filings and, for brokers, a surety bond. It can be revoked, and revocations are public.
Authority is the thing you actually risk with a serious compliance failure. Fines cost money; losing authority stops the business.
Related
Inteleri works out what a load actually pays you once things like this land. See how it works.