What is the difference between used and pre-owned games?

A used game is a game that has either been returned with a problem, or has been returned within 120 days of purchase for a fraction of what you paid for it. A pre-owned game is a game that has been returned within 30 days of purchase with no problems or a game that had opened by an employee and tested. Pre-owned games, for the most part are the better purchase.

Rules of Gamestop in US