What is the GUI difference between Windows and Linux?

There are many differences between the Graphical User Interfaces of Windows and Linux. There are similarities as well.

To be exact, Linux, itself has no GUI per se. The GUI(s) that you can use, and there are literally hundreds to choose from, are separate programs running under Linux.

[speaking simply here]Linux itself is the core (kernel) of the Operating System, whereas the GUI, the file managers, web browsers, chat programs etc, are all applications that give the OS "features".

With Windows you only have the included GUI, that is unless you install a modification such as WindowBlinds(TM).

Linux, and many other POSIX compliant OS's can use many GUI, here is a brief listing and some links to GUI sites.

KDE - The K Desktop Environment: http://kde.org/Gnome (Pronounced with a hard "Guh" as in Guh-Nome: http://gnome.org/Enlightenment: http://www.enlightenment.org/blackbox: http://sourceforge.net/projects/blackboxwmAfterStep: http://freshmeat.net/projects/afterstep/ and many more...