+P and +P+ are higher pressure and higher velocity.
Glocks will shoot these forever. I run nothing but +P+ factory and reloads in my Glock and my SIGs.
My G-17 has digested over 12000 +p and +P+ and shows no signs of wear.
And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.