The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
Two or more freely interacting individuals who share norms, share goals and have a common identity form a group.
That is why people gather together in groups. Because they have similarities and common values. They enjoy to stay together, talk, exchange ideas and support each other. If this group goes one step beyond, we would have been talking about a formal group that was formed to do a specific task productively. Commonly, these groups are part of organizations and are directed by someone who is the leader.
