Chests give you free stuff, each chest contains cards to help you collect and unlock items in game, including cues, masks, ballsets, decals and more. There are also coins and Gems in there too!
If you have a chest ready to open, it will be displayed on your home menu (see first highlighted image below)
Selecting X on the home menu will take your to your chests:
In the example below you have mutiple chests ready to open.
FREE CHEST - is a daily chest that you get for free just for coming back to play
X4 STANDARD CHEST SLOTS - this is where you will find your reward chests for winning matches etc. if a chest is ready to open simply press A to open it and collect what is inside.
If you want to collect more than 4 chests at once you can buy more slots.
Chests have different values depending on if you win a wooden, silver, gold or platnum chest. The higher up the Tours the better chests you get.
Happy playing and collecting! :)