The Daily Login Bonus is a feature implemented in Brave Frontier Global to give out FREE in-game items in an engaging way. In summary, each day that you log into the game you will be given a chance to pick a Treasure Chest as shown in the image above. Upon choosing one, you will be given a random loot or bonus reward based on the chest that you have chosen.
The most interesting part of this feature is the more that you login into the game in consecutive days, there is a better chance for a better reward, since the rewards are bracketed into 9 tiers.
If you want to know more about this great Global Exclusive feature you can read this article.