It is important to pay attention to both types to know the difference. Gangs develop for a lot of reasons. Most commonly they start out as a social group. The gang develops when criminal activity begins. This criminal activity is often larceny or assault used to prove worthiness to be included in a gang.
Kids join gangs as a replacement for the family.
Kids join to belong. The most common reason for joining a gang is protection. Structure and discipline provided by the gang provide a sense of security. The more attention we pay to gangs teaches us that they are getting younger. We are not allowing denial to blind us to the fact that young children are gang members.