The three types of social groups are primary, secondary and reference groups. A social group is defined as a collection of individuals who interact and share a sense of unity among each other.
A primary group is a small social group that contains personal and long-lasting relationships. Family is the most common primary group, but marriage or any relationship that is long-lasting is a primary group as well.
Secondary groups are large groups that revolve around institutional and formal relationships, such as those with classmates, teachers or business associates. The foundation of the primary group often begins within secondary groups. A reference group is a social group that serves as a basis for decision-making, such as a peer group, a club or a team.