Originally, the mechanical components in a tape recorder that move the tape past the record and playback (or write and read) heads. The transport controls all tape motion during recording, playback, fast forward and rewind. On professional recorders, the jog, shuttle, and scrub controls are also part of the transport mechanism. The mechanism also includes tape guide pins, capstan, pinch rollers, and tension controllers.
A transport contains no electronics itself for encoding or decoding the information recorded. So, the transport mechanisms for analog and digital tape recorders are essentially identical. The term is sometimes used to describe a mechanism that moves any media, including floppy disks, hard drives, and optical discs.
Transport controls, record, play, stop, rewind, and fast forward, became highly standardized over the years, and now can be found on virtually every hardware and software DAW and sequencing application despite the fact that there is no actual tape to move.