With other operating systems, if they have a graphical interface (which most do these days), you don't get much of a choice. Sure you can configure parts of the graphical interface to work the way that you want but the overall interface and how it works is fixed by the operating system.
The same is not true of Linux. With Linux you have a plethora of graphical interfaces to choose from each of which functions differently. Sure there may be similarities in the ways that some of the different graphical interfaces work but each is in fact a completely separate interface. In all cases, the functionality that provides the graphical interface for Linux is called the Xwindows system and it can either be started automatically on starting linux or later manually using the command startx.
In fact, the graphical interface for Linux exists in three separate layers (each of which performs a different part of the functionality) and with each of these three, you get a choice of which particular one of several or many alternatives that you are going to install.
The first layer (closest to the operating system) is the X Server. The X server provides a communications channel between the graphical interface and the operating system. Unlike other operating systems where the window displaying the results of the execution of a program appears on the screen of the computer running the program, the X server can channel communications between a program running on one computer and the graphical interface on an entirely different computer. Some common X server distributions are XFree86, Metro-X, and Accelerated-X. The X server will be installed when you install Linux and you should not need to worry about it again until you are ready to upgrade to a later version.
The second layer of the Linux GUI is the Window Manager. The Window Manager (as you would expect from its name) is responsible for managing the windows displayed on the screen. The border of the window, the title bar (and any buttons that it contains), and the functionality of the window itself (close, maximize, minimize, resize, move, etc) are handled by the window manager.
The window manager is not responsible for the content of the window. That is looked after by the Desktop Environment. Usually, the window manager and desktop environment come together so that a particular desktop environment is always run on the particular window manager but this does not have to be the case. For example early versions of the Gnome desktop environment came with the Enlightenment window manager but recent versions of Gnome are now supplied with the smaller Sawfish window manager.
One thing that is very different between the Linux graphical system and other operating systems is that you can install more than one desktop environment and window manager and select between them when you log onto the system. Linux is a multi-user operating system so this means that if your Linux system has five people who log on to it then each can have their own preferred GUI that they use and the screen on each computer attached to the network may look completely different even when they are all running the same programs. Because you can select between GUIs when you log on, there is also nothing to stop a single user from selecting a different GUI to use each time that they log on.
Different window manager / desktop environments can differ considerably in their user friendliness, complexity, and size. You may want to experiment with using a number of different desktop environments on Linux in order to find the one that best suits the way that you like to work. Two of the most popular desktop environments are Gnome and KDE and these provide the most complex, largest, and most user friendly of the desktop environments (that I am aware of). There are other simpler, smaller, but perhaps initially harder to use window manager / desktop environment combinations out there as well and some examples of these include WindowMaker, BlackBox, Ice WM, Sawfish, Enlightenment, AfterStep, Fvwm2, and Fvwm1.
As with everything about Linux, there are lots of choices, and the final decision of which to use is up to you.
This article written by Stephen Chapman, Felgall Pty Ltd.