Free Game of the Day is a free app that highlights a free game each day. You download the game app from within the Free Game of the Day app. This is because many of the apps that they make available are ones that you'd normally have to pay for. It's an interesting marketing model: they convince developers to make their game available for a day for free. This brings attention to their game, and downloads soar, boosting their ranking. In the case of the Stair Dismount game, it went from 5,000 daily downloads to 32,000.