In computing, a server is a computer program or device that provides functions for other programs or devices. It is called a "client". This architecture is called client server model, and a single overall calculation is distributed over multiple processes or devices. Servers can provide a variety of functions, often referred to as "services," such as sharing data or resources between multiple clients, or performing calculations for clients. A single server can serve multiple clients, while a single client can use multiple servers. Client processes can run on the same device or connect to servers on other devices over the network. Typical servers are database server, file server, mail server, print server, web server, game server and application server.

Today, the client server system is most often implemented by the request response model (and often identified by the request response model): the client sends a request to the server, and the server performs some operations and sends the response back to the client, usually with results or acknowledgments. Specifying a computer as server level hardware means that it is dedicated to running the server on the computer. This usually means that it is more powerful and reliable than a standard personal computer, but instead, a large computing cluster may consist of many relatively simple, replaceable server components.