================================== I think what you're looking at is a cut-off guard with some kind of depth stop. Most angle grinders have a simple cut-off guard (i.e. without depth stop) like the one on the left of that page. The guard has a dual purpose - to protect your hands from accidental contact with the grinding disk and to direct the debris stream in a particular direction away from the operator.
The guard can be moved to different positions to suit the cutting angle. You can experiment with different positions to find the best position for your cutting style.
Cic.