Its simply work as advertisement. The higher the ranj the higher exposure of the project design called signature. From these design codes embedded and directly linked to their social and sites. There are different terms for signature some are paid per post and some are weekly depends on the manager.

You can see a lot of samples of these campaigns on service section. More projects are usually handled by reputable manager and based on the users or participants quality post before he can join such campaign. Are you willing to do one or join one later on?