Beginner, Intermediate, and Advanced — unlocked by points.
Your stage shows how far along you are. Everyone starts at Beginner. By default you reach Intermediate at 500 points and Advanced at 1,500 points.
The progress bar next to your stage shows how many points you need to reach the next one. Reaching a new stage also unlocks the matching track in the main course.
Related: Why is a track locked?, How points work