The X Window System is a networked display system. A server component, the X server, is responsible for coordinating between all of the clients connected, taking input from the mouse and keyboard, and pushing pixels on the output. The most popular X server implementation is the Xorg X server, developed by the X.Org Foundation and community. There are other X server implementations: you might remember that Xorg was forked from XFree86 a decade ago, that Sun Microsystems has had several X server implementations, in both Xsun and XNeWS. Today, Xorg is the dominant X server implementation, getting most of the development. But back in the day, multiple competing implementations existed.