The hex socket screw, also known as the socket head cap screw, is a headed and externally threaded part designed for insertion through a close tolerance internally tapped hole and mated with a nut. Tension on the hex socket screw is induced by rotation of the screw head. There is a hex socket in the head that accepts a hex wrench to tighten the socket head cap screw. The point at the threaded end of the socket head cap screw is machined flat so it will fit into a drilled hole.
Head/drive combinations of hex socket screws are either standard no-head with just the hex socket, flat head hex socket, or button head hex socket.