desktop environments / x / window managers?

Have I got this right?

* X is the graphical server for linux.
* you run window managers on top of X, window managers can be minimal (blackbox) or fuller featured.

So, what are Gnome and KDE?  Are they a combination of WM and extra software, or are they just feature rich WMs?

To be exact, X consists of three parts:

* X-Server is what controls the graphics card and input devices on a particular computer
* X-Clients are any applications wanting to draw themselves on a screen
* The protocol that X-Clients and Servers use to communicate

With that architecture it's perfectly possible to have X-Clients running on a different machine than the X-Server. "display" and "XDMCP" are some keywords for a search.

Also, desktop environments typically also bring their own session manager which restore you previous session (running applications, window placement, etc) once you log out and in again. The only "pure window manager" that does that as well that I know of is Window Maker.