What are the stars below your name?

[Lewwings]

They are gained through the amount of forum posts. I am not sure how many posts you need for each star, however to get 5 you need 1000 posts.

Forum rank also has an influence on the amount of stars below your name that you have. 

For example, Teachers have 5 whilst Admins have 6, these are set automatically, probably via the AdminCP, as when you edit a rank, there is an option to set the amount of stars per rank/classification.