We're removing Missions in June 2020. See here for more information.
The mastery system helps us understand what you know and what you still need to learn so that we can personalize your learning dashboard.
For instance, we’ll recommend skills for you to practice based on what you’ve learned so far. The goal of these recommendations is to help you focus your time on skills that you’re ready to learn but haven’t mastered yet.
As another example, we’ll personalize your mastery challenges to make sure you have the chance to review skills you’ve already learned.