Here, you will be presented with various rewards that you can claim.
To unlock them, you will need to complete challenges, you can view these by tapping the "Challenges" button in the top-right.
The free rewards at the top are accessible to all, but to access the golden rewards shown at the bottom, you will need to purchase the Gold Pass.
This pass only lasts one season (the remaining season time is shown in the top-left corner), and any unclaimed rewards will be lost, so be sure to claim these rewards whenever possible.
You can access this menu by tapping the relevant button in the bottom-right corner of the main menu.