Greasers were a youth sub culture that started in the 1950s among teenagers. In the northeastern and southern United States. They often listened to rock and roll music and there style was influenced by Elvis Presley. Greasers usually wore white t-shirts and leather jackets and also blue jeans.
A teenager might have joined a gang in the 60s because, they came from a bad family or because it was there only way to escape their problems. The turned to gangs because it made them feel like they had friends.