Sockets are a key part of Unix and Windows-based operating systems. They make it easy for software developers to create network-enabled programs. Instead of constructing network connections from scratch for each program they write, developers can just include sockets in their programs. The sockets allow the programs to use the operating system's built-in commands to handle networking functions. Because they are used for a number of different network protocols (i.e. HTTP, FTP, telnet, and e-mail), many sockets can be open at one time.
http://compnetworking.about.com/od/itinformationtechnology/l/bldef_socket.htm
sockets / WinSock
By Juergen Haas, About.com Guide
Filed In:Linux
Definition: sockets / WinSock: In programming, the "sockets" interface is the most common way that coders use to access the network. Sockets works by creating a "file handle" that when written to, sends data over the network rather than to a file on the hard-disk. Contrast: Other interfaces programmers could use are higher-level abstractions like RPC, or lower-level "raw" interfaces like libnet. Contrast: Sockets originally came from UNIX, but has been ported to other platforms. In particular, the "WinSock" variant for Windows includes both the UNIX-style functions as well as the Windows-style functions. It is possible to write sockets-based programs that compile for both platforms. Key point: The name "sockets" comes from the TCP/IP term "socket". A socket is minimum information necessary