With the Game Agent, Aspyr has created an external application to browse and buy games from their online store. The application, which only works if you're connected to the Internet, connects to the Aspyr store and lets you easily look around and view games profiles. You'll find links to the website in case you're interested in buying a game.
Every time you're looking at a game description page, you'll notice that the program features a requirements section at the bottom. This will allow you to see, by way of green check marks or red crosses, if your Mac meets the requirements for the particular game. Click on the "i" button to change the settings and adapt them to your Mac. Aspyr also lets you select any Mac model from a drop down menu and see if it can play the game in question.
Aspyr Game Agent is a handy tool to check what games can play on your Mac and buy them directly from the games distributor.