A glass screen protector cannot be compared with a normal screen protector. Where a normal screen protector consists of a plastic adhesive plate, a glass screen protector is a hardened piece of glass. This forces the screen protector to absorb the forces that are exerted on your mobile, for example due to a fall. This will not crack the screen of your mobile, but the glass screen protector.
You can then simply subtract the glass screen protector from your screen and then install a new one. The advantage of this is that you don't have to put a new screen on your phone if you drop it, just a new glass screen protector is enough. Simple, fast and cheap.