With today's servers and personal computers, it is hard to imagine not having a graphical desktop. The ability to "point and click" your way around the desktop and configuration menus has made it possible for non-computer geeks to manipulate these machines. In addition, it has made the computer administrator more powerful than ever. Unlike other OSs, under which the graphics are a core part of the OS, Linux, like UNIX, uses an application known as the X server to provide the graphical user interface (GUI). This server process could be thought of as being just like any other application that uses drivers to access and control hardware. With today's desktop environments, a single computer can use multiple monitors along with multiple virtual desktops. Something that makes X stand above the rest is its innate network design, which enables remote machines to display their programs on a local desktop. The X server is a client/server modeled application that relies heavily upon networking. In this chapter, we cover Linux's implementation of X along with some troubleshooting techniques, and we illustrate key concepts using a few scenarios.