How do I recognize Extra Ammo and PXItems ?

What's PXItems and Extra Ammo and also how do I recognize that I have them in the game ? (I'm using no-menu hack).
I know what is Extra Ammo but whata hell is PXItem?
Thanks

PXItem >> Bandage 1, Bandage 2, Bandage 3, SniperX1, SniperX2....