GameStop has long offered trade-in promotions so that consumers can buy new video games with credit they receive for letting the shop sell any older games they've stopped playing, but changes to the store's policy will hopefully give you more money.
The company hopes to simplify the current trade system to account for baseline expectations of what you can expect to receive for each game you trade in. Consumers will get less when they take cash for their trades, as has always been the case but hopefully overall trade values will rise.
If you've got a Powerup Rewards membership with the retailer, you'll still get bonus credit on everything you trade. In all honesty, it doesn't seem like much is changing here other than the way trade promotions work.
Typically, GameStop had offered 30% added trade value when you put your credit towards a preorder or new product immediately. Other promotions included added cash or set values when trading games from a list or multiple games at the same time. This doesn't sound like a total negation of those programs, which did net added trade value when used and calculated properly behind the register.
Still, it'll be interesting to see exactly what kind of change the company expects from this policy shift. For more, Kotaku has obtained several internal documents and e-mails regarding the trade-in program update.