Chassis-Mount monitors - like the Open-Frame version - are mounted from behind, but they do have a bezel.
Chassis Monitors have a bezel, and are suitable for free-standing applications. They can be mounted using the VESA sockets on the rear side.
Panel-Mount monitors are mounted from the front into a cut-out in - for example - a switchbox. The mounting screws are invisible and are attached from behind.
Flush-Mount Monitors - like the panel-mounts - are mounted into an existing cut-out. The mounting screws are visible and inserted from the front.
Rack-Mount monitors have front handles and edge-holes suitable for mounting in 19" or other standard rack systems.
Zero-Bezel monitors have a plastic bezel integrated with a glass screen, for use where a more stylish appearance is desired. The chassis model is for free-standing or wall mounting.