Ammo that has been loaded to a higher internal pressure than standard ammo. The higher pressure produces a higher muzzle velocity and theoretically has more stopping power. Before you fire +P rounds through your gun, make sure your gun can handle it. I think most newer models are ok but older models may not. Read the owners manual. +P rounds are more expensive so you're probably not going to burn off many rounds at the range using them but they are more for defensive purposes. Again - check the owners manual to make sure your gun can handle them.