A transport is a starship or other vessel dedicated to transporting cargo or passengers.
Starfleet has operated various manned and unmanned classes of transports, usually featuring warp engines of the current military standard fitted to special-purpose high-volume hulls. Transports range in size from small two- or three-manned ships to huge starliners capable of carrying tens of thousands of people if needed. A transport is not to be confused with cargo carriers or freighters, a term commonly used for sublight bulk cargo drones.
Non-canon, but presumed to exist.