A socket is a specialized connection point that can be used for interprocess communication (often termed UNIX sockets) or other generalized communication such as over a network. Sockets are not dependent on the protocol used. They are largely talked about in terms of networking.
The majority of data flow on the internet uses sockets.
Some details on Socket programming:
- UNIX: http://www.faqs.org/faqs/unix-faq/socket/
A Socket FAQ: