These codes allow you to support content creators every time you make an in-game purchase, and you get rewarded with goodies and special invite rooms in return.
War Thunder is a free-to-play multiplayer game all about ... based shooter with the mayhem of a team-based FPS to create a wacky game show where the winner comes away with loads of cash.
So when its creator recommended two other "special ... "I have played both previously and LOVED them, and both have a free demo you can play right now! Go support some cool indie devs!" ...