What is a DE?
A DE stands for Desktop Environment. A WM stands for Window Manager.
I suppose I'll go over DE first; a Desktop Environment basically comes with apps, your comp manager, your window manager, and some apps that you can use for modern day usage. Um, I believe many distros come with a DE pre-installed, because it's pretty easy to use in general.
A WM, is a bare-bone desktop environment that only includes the window manager. Some aspects of a WM are unique, and they can be replaced over the existing WM in a DE. People who use stand-alone window managers have to go through a slightly harder process, which is first setting up a way to switch throughout your apps, like a panel, or a dock. Next you'll need a way to launch those apps, usually by a right-click menu which is most of the times pre-installed, or you can just find some other weird way to do it. I believe Docky has an application manager applet? Anyways for a basic stand-alone window manager with the most general experience you can get is a panel, and an application launcher. Next you can add effects on top of it, like downloading comp manager such as compton (i like this one). If you want more cool stuff, like wallpapers, etc., I just recommend you stay with a DE, because everything in a DE is designed to be simple for you.
EDIT:
NiXiLL, you might wanna check this out if you hate the debian systems:
http://www.deviantart.com/art/Pantheon-Under-Arch-V0-1-446682189:o
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