Yes, Gift Codes. The ones u redeem and get rewards. The rewards should range from Silver Boxes, Coins and Gems, Power Kits, Free Epics Etc.
Examples:
SuperMechs = 2 Silver Boxes
Upgrade + Rare Power Kit Lvl15
Purple = Random Epic
Btw: If u don't like these, it's ok, these are for the Noobs (like me)