The ratchet wrench consists of two main parts: the handle and the socket. The handle is the wrench itself. The part you hold in hand and turn to tighten or loosen the fastener.
At the end of the handle is a square-shaped projection called the driver. The driver accommodates the socket.
Ratchet is used to drive sockets. Typical sizes are 1/4", 3/8", or 1/2".