What do we call a group of people who share a common interest, identity, or beliefs?

The term that describes a group of people who share a common interest, identity, or beliefs is "in-group." This concept in social psychology refers to a social group with which an individual identifies and feels a sense of belonging. Members of an in-group often share similar characteristics, values, and attitudes, which fosters a feeling of community and solidarity among them. The idea of belonging to an in-group can significantly influence one’s self-perception and social interactions.

Understanding the notion of in-groups is essential as it contrasts with out-groups, which consist of individuals who do not belong to that particular group and may even be viewed with skepticism or prejudice. Reference groups serve a different function as they are utilized by individuals for self-evaluation rather than being groups with which they identify. Social categories, on the other hand, are broader classifications and do not necessarily imply a shared identity or belief system among individuals. Thus, "in-group" is the most fitting term for a collection of individuals who possess shared attributes.