A PPSh (I always get the caps wrong) is a WWII era Soviet submachine gun.
This pic. is from Oleg's site...
It was, by and large, the standard armament for the majority of the Soviet military in World War II. Entire units were armed with these, and a few other variant, submachine guns.
Incredible short-range firepower.
In a lot of ways the PPSh can be thought of as the Russian Thompson, although it was far more widely distributed than the Thompson. It had, however, the same sort of public cachet and it became almost universally associated with Soviet troops right through the 1960s when the AK-47 really started entering the public eye.
Hey, here's a link to what looks to be a very good website on the PPSh:
http://www.ppsh41.com/