A system forms sub-groups from a given user group of a social networking system and form descriptions of the sub-groups that provide an intuitive understanding of sub-group composition, such as likings of the sub-groups. In one embodiment, a given user group of a social networking system is clustered into a plurality of sub-groups, and representative characteristics—such as the characteristics of a composite or actual member of the sub-group—are determined for each sub-group. In order to form sub-group descriptions, a set of objects, such as pages of the social networking system, is ranked with respect to the representative characteristics of the sub-group. The highest-ranking objects for a sub-group are then used to form the description of that sub-group. For example, the topics associated with each of the highest-ranking pages can be combined into the sub-group description.