I've written an application that puts the stats from PokerTracker on the screen. It's called PokerAce Hud and you can download it here:
http://pokeracesoftware.com
There are also two other applications that do nearly the same thing, GameTime+ and PlayerView. You could do a search if you are interested in either of those two.
The stats that people use when they identify a player as x/y/z are x = VPIP, y = PFR and z = Total Aggression Postflop (no preflop numbers included).