There are two basic customer group types available. Discount customer groups and access customer groups.
Customer groups can be created to set discounts for customers, depending on their group membership. Discount customer groups can be set manually or be assigned automatically when a customer signs up for a discount membership.
The discount of discount customer groups can be calculated in two different ways: The discount can be either a discount to the normal product price or a markup to the supplier price.
Customer groups can also be set for access to certain products and or categories. Only customers with the assigned access group are able purchase the products that have this access group assigned
A visibility option allows you to either completely hide the categories and products for customers who are not members of the specific access group or have them visible for all customers and just prevent them from checking out with those products.