Why are Android "skins" called "skins" at all?  To me, "skin" is interchangeable with "theme" and is (pardon the pun) only skin deep - a visual alteration with no functional difference.  Android "skins" however are, from what I can tell, the same idea as what's known as a "desktop environment" on Linux - a complete experience, including a unique GUI, unique features and functions, and a whole suite of applications designed to work with it.