The daily chest can be gotten after you complete a daily mission. Once you have one, you can click on it to craft keys.
5 Bronze bars (+ 1 gem, optional) = 1 Key
The higher tier Gems get you more chest slots. The number of chest slots determines how many different types of items you get.
Once you have a key, you can use it to open the chest.
Reward scales based on account levels and key used.
The following is loot found by players. Please remember that loot is leveled.