They database (is that a verb?) stats on players you encounter in ring and tournament games. You can separate your databases accordingly. You can get them for Hold 'Em, Stud, Omaha. They allow you to see patterns in your opponents, analyze how aggressive they are, what types of decision they make in certain situations, etc. They cost around $70 bucks or so. Definitely worth it. Great fun to look back at a session and figure out what you did right or wrong, where you might tweak your own play in the future to improve your wins/minimize your losses.