A computer server is an electronic machine that exchanges data with other machines via wireless or wired connections. It is the workhorse of the Internet, and enables worldwide communication between distant machines.
When an Internet address is typed into a browser on a local machine, a request is sent to the server of another machine. If the server is online and functioning correctly, it returns the requested information in the form of a Web page. The entire interaction is described as a client-server relationship; the local machine is the client, and the distant machine is the server. The roles of the two machines are interchangeable.