A server is a member of a class of programs in a modern software architecture paradigm called client/server software architecture, in which all applications have two components: the client component and the server component. The server component typically has the following characteristics:

• A server is most often centralized, usually on a large computer (a client usually runs in multiple instances on desktops or other small stations throughout a network.)
• A server is passive; it does little or nothing until it receives an explicit request from a client to do something. (A client is active since it's a tool in the hands of a human).
• A server usually runs continuously waiting for requests, while a client runs only on-demand (when invoked by a human).
• A server usually runs in the background and interfaces only with other software (clients), and rarely interfaces directly with humans (whereas a client is usually invoked by a human and takes commands from a human).
• A server must handle multiple tasks concurrently since many clients may be requesting it's services simultaneously. A client usually works for one person and does one thing after another in sequence, as the user commands it.

For a list of common information servers on the Internet, see our Introduction to the World Wide Web. [an error occurred while processing this directive]