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.