Q: What are the various session options for public Debathena machines?

Answer

The login screen contains a Session button that allows you to select different types of login sessions. Normally, you won't need to use this button, but on rare occasions, you may want to select a different type of login session for troubleshooting.

Last session: The last session you used.
System Default Session: The standard Athena login session. You may select this session to revert to the defaults if you previously chose a different session. Currently, this default session is a GNOME session.
GNOME: The GNOME desktop environment.
Login Without Customizations: Standard Athena login session, ignoring your customizations ("dotfiles"). You should select this option if you experience errors when attempting to login using the Default Session.
Dwm: A minimal, keyboard-centric window manager intended for advanced users. If you find yourself in a Dwm session, you can press Alt-Shift-Q to logout.
KDE: The K Desktop Environment, a common alternative to GNOME.
Twm: The TWM (pronounced "twim") window manager is one of the oldest window managers in the UNIX world, and is often preferred for its simplistic functionality. You can click the left mouse button on the black background to get a navigation menu.
Window Maker: A window manager that resembles the GNUstep and NEXTstep environments.
XMonad: Like Dwm, this is a minimal window manager intended for advanced users. As with Dwm, you can press Alt-Shift-Q to logout.