Window managers are X client programs which are either part of a desktop environment or, in some cases, standalone. Their primary purpose is to control the way graphical windows are positioned, resized, or moved. Window managers also control title bars, window focus behavior, and user-specified key and mouse button bindings.
Four window managers are included with Red Hat Enterprise Linux:
kwin — The KWin window manager is the default window manager for KDE. It is an efficient window manager which supports custom themes.
metacity — The Metacity window manager is the default window manager for GNOME. It is a simple and efficient window manager which supports custom themes.
mwm — The Motif window manager is a basic, standalone window manager. Since it is designed to be a standalone window manager, it should not be used in conjunction with GNOME or KDE.
twm — The minimalist Tab Window Manager, which provides the most basic tool set of any of the window managers and can be used either as a standalone or with a desktop environment. It is installed as part of the X11R6.8 release.
These window managers can be run without desktop environments to gain a better sense of their differences. To do this, type the xinit -e <path-to-window-manager> command, where <path-to-window-manager> is the location of the window manager binary file. The binary file can be found by typing which <window-manager-name>, where <window-manager-name> is the name of the window manager you are querying.