Memberships allow you to put your Members into different groups.
You setup several memberships and each Member belongs to one of the memberships.
Memberships can be free, or have different prices.
Each membership can be setup with unique or shared content allowing you to have pages, banners, etc only usable by specific memberships.
The header/theme/content of every page in the members area can be customized for each membership.
When logged in as the admin go to "Memberships". On this page you can add new membership as well as edit/delete existing ones.