Openbox is a standards compliant, fast, light-weight, extensible
window manager.

Openbox works with your applications, and makes your desktop easier
to manage. This is because the approach to its development was the
opposite of what seems to be the general case for window managers.
Openbox was written first to comply with standards and to work
properly. Only when that was in place did the team turn to the
visual interface.

Openbox is fully functional as a stand-alone working environment,
or can be used as a drop-in replacement for the default window
manager in the GNOME or KDE desktop environments.