Desktop managers are for wimps who want a point-and-click, drag-and-drop interface for manipulating files and launching programs.
The window manager is a special X app that does things like draw the titlebars and borders around your window, and they also provide menus that are bound to your mouse buttons. Some do a lot of other things, but for some it's little more than this.
If you want to see X with no window manager, run this command:
X :1 & sleep 5 ; xterm -display :1
A very bare X will start up and a few seconds later you'll get one xterm with no window decorations.
From here you can type commands in the xterm. For instance, you could start a window manager.
Use ctrl+alt+function keys to switch between this and your other X session which you probably have up right now.