Glossary Entry: Server

Servers are programs that listen for and respond to requests made by other programs, known as clients.

Take a web server for example. A client, such as your web browser, can ask it for a copy of a file, and the server will reply by sending the file along with some information about it, such as whether or not the file was actually there.

Also, the term "server" can also refer to a computer that only runs the server program. If you've ever heard of a server being down, this is likely how the term is being used.