The GUI family tree
Without getting into a lot of technical jargon, in order for those nice windows (yes, with a small 'w') to appear on your computer screen, you have to have some graphics libraries installed on your computer. These libraries determine how a window is to appear, what it is supposed to look like and what the buttons and menus are supposed to do. That fact that you can use GUI based computing under Linux goes back to the time before Linux was even thought of. In the mid-eighties at the Massachusetts Institute of Technology they came up with the X window system. By 2002 standards it was a primitive GUI system to run programs with. The main idea behind this actually came from an earlier project at Xerox called WIMP (Windows, Icons, Menus, Pointer), a project that essentially started the idea that computers could be used in an attractive graphical environment. 1
The 'X Window system' provided the libraries to make the frames, buttons and menus that make up a window. Development of X Window still continues under the auspices of the X Consortium. In 1992 the XFree86 Project was started. This aimed to develop a free version of the X Window System. There have been several versions of XFree86 and the current stable version at the time of this writing is XFree86 4.0. Though there are other equivalents to the libraries that XFree86 offers, it is by far the most widely used window system under Linux. Any attempt at using Linux as a desktop operating system to get "productive" work done (word processing, spread sheets) or to entertain oneself (play games, listen to music, watch TV) will start with the installation of XFree86.
With major distributions, the install process takes care of getting XFree86 on to your system. There are two parts to this. One is installing XFree86 itself. The other is installing the X server that goes with your particular hardware. The X server is just the means of getting XFree86 to work with the graphics card that you have in your computer. For example, if you have a graphics card from ATI, then you would install the XFree packages along with the X server package for ATI. If you have an S3 card, then XFree86 and the X server for S3 cards should get installed. I explain this because some distributions do a pretty fine job of getting you up and running, but you may get asked what graphics card you have when you do a more interactive type of install of Linux. In this case, you have to know what card you have so the correct X server gets installed and you can have a graphical environment to look at after the install process is finished.
Recently, major Linux distributions will also offer you the possibility of getting right into the GUI when you turn on your computer. This is done by way of the program XDM. This is the Microsoft Windows influence on how things are done that I mentioned before. Traditionally in Linux, you would turn on your computer and get the black screen and the command prompt. Then you would type:
startx
and your graphical environment of choice comes up. 'Choice' is the key word here. By having the command prompt and then issuing a command to start the GUI, you can switch into any number of desktop environments "on the fly". Of course, if you're not interested in having more than one, then you can use XDM and have your favorite desktop there waiting for you.
Regardless of the way you choose to start up your machine, before you see your desktop utilities of choice, we're going to have to configure XFree86 to use your monitor, mouse and keyboard. That is, whether you type startx or not, we'll have to come up with a configuration so we can, in fact start X.
1 The X Window User HOWTO by Ray Brigleb, 1999

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