A jack is a receptacle into which a plug is inserted to make an electrical connection. That is, it is the female half of a connector.
There are numerous types of jacks for various computer and other electronics applications. They vary considerably with regard to size, number of electrical contacts, physical connection method, materials and other characteristics.
Multiple types of jacks can be found both inside of and on the backs of computers. Jacks are also an important component of networking devices such as hubs, switches and routers, which use jacks compatible with RJ-45 plugs. The jacks for telephone circuits that are built into modems, walls, telephones, fax machines, etc. are compatible with RJ-11 plugs.
The term socket is a synonym for jack when both are used in an electrical context. In a computer context, a socket is also one end of a type of inter-process communication (i.e., a bi-directional communication link between two applications) that can occur either on the same computer or over a network.
Created October 26, 2005.