A socket wrench is a tool used to tighten and loosen nuts and bolts. It consists of a ratchet handle, a socket, and a drive size. The socket is attached to the ratchet handle, and the drive size is used to attach the socket to the nut or bolt. Socket
From Wikipedia
A socket wrench is a type of spanner that uses a closed socket format, rather than a typical open wrench/spanner to turn a fastener, typically in the form of a nut or bolt.