In a simple analogy, think of a gang member as a cancer cell. A gang member may move to another state, and infect new members. As more people are infected and join the gang, the progression grows from a single cell to a tumor. The tumor eventually infects the entire body. Many gangs are involved in illegal criminal enterprises.
Profits can be considerable, and are a powerful incentive to recruit new members.
Gang crimes commonly seen include sales and distribution of narcotics, assaults and drive-by shootings, burglaries and other property crimes, extortion, and auto theft. New members are usually middle-school age or older. They may come from any ethnic or societal background. They often have poor self-esteem, have experienced little adult guidance and participation in their lives, and lack a sense social responsibility. They may join a gang for excitement, attention, responsibility, recognition, financial profit, peer pressure or family tradition, or a combination of these factors.