"The X Window System is a network-based graphics window system that was developed at MIT in 1984. With X you can work with multiple programs simultaneously, each in a separate "window". One of the strengths of a window system such as X is that you can have several processes going on at once in several different windows (perhaps even on different machines). These windows are controlled by a resident "window manager".

Most window systems are closely tied to the machine's operating system and can only run on that system. The X Window System, however, is not part of any operating system, but is comprised entirely of user-level programs.

The architecture of the X Window System is based on a "client-server" model. The system is divided into two distinct parts: "display servers" and "client programs". Acting as intermediaries between client application programs and local display hardware, display servers provide capabilities and keep track of user input. Client programs are those application programs that perform specific tasks and make requests communicated to the hardware display by the user.

This division within the X architecture enables the client programs and display servers to work together on the same machine or to reside on different machines connected by a network..."