Classes are groups of members that have different sets of rights. For example, some non-profits have voting and non-voting classes of members. 

If you aren’t sure whether your non-profit has member classes, check its articles and bylaws. If a non-profit has more than one class of members, it is required to describe each class and their respective rights in the articles and list the conditions for membership in each class in the bylaws.

Note that this does not refer to different categories of members (e.g. family and individual memberships; gold and silver memberships) unless there are different rights associated with that category.