Please forgive my ignorance here but I an trying to find information regarding Themes. I am relatively new to Linux and have been using Egdy Eft for about 1 month now.

I have been trying to customize my desktop but I don’t fully understand some of the themes t such as:

GTK 1.x
GTK 2.x
Metacity
Compiz
Beryl
GDM Themes
Splash Screens
XMMS Themes

Perhaps someone could explain there to me or direct me to where I could research them.
Also I was wondering how it is that you can make your windows transparent so that you can still see the wallpaper behind?

GTK 1.x & 2.x -- I believe these are programming libraries primarily developed for programs running under the Gnome Desktop
Metacity -- Window Manager for Gnome Desktop
Compiz -- 3-D desktop effects/window manager
Beryl -- Fork of Compiz because they wanted to do things a little different
GDM Themes -- GDM is the graphical greeter (login screen) for Gnome desktops. KDE typically uses kdm. Generic X uses xdm.
Splash Screens -- Progress bars, etc during the loading of the OS.
XMMS Themes -- I believe XMMS is a music player.