Level Quest tracks your XP earned from playing and building. The higher your level, the more rewards and status you unlock.

How to get to the "Level Quest Page"

When you progress a level you are automatically taken to the level quest page. If you want to check out your level by yourself click your player profile picture on the top left to open up your player profile. That displays the player level as follows. 

If you click on you player level here, you are taken to the "Level Quest" page.  As you collect more XP , you will keep progressing your level and earn the displayed rewards.