socket wrench

A type of wrench (spanner) featuring multiple removable and interchangeable socket heads (sockets), each designed to fit a particular size of bolt head or other fastener, which can be attached by the drive to a ratcheting handle, breaker bar, or other driver.

Any wrench, including a nonratcheting one with an integral (nonremovable) head, that has an internal/concave feature (a socket) that engages the head of an external-wrenching fastener.