A group of sockets used to manually connect incoming and outgoing lines together in communications and electronic systems. Using short patch cords, one end is plugged into an "in" line and the other end to an "out" line. Wireless patch panels are also available that provide the cross connections by flipping a switch rather than plugging in wires. See wiring rack
and patch cord
Rack Mounted Patch Panels
Patch panels come small and large. In large datacenters such as this one, patch panels are often rack mounted. Not remarkably high tech, they are simply used to manually connect one line to another.