Cliques are casual associations of kids, generally with the same interests. Teens in cliques spend time together at school and spend some time at home together, but it is not an obsession. And they have other interests and connections. Gangs require a more intense affiliation, with strict rules and dress codes. They begin taking over the teen's life.
Members can wear only certain colors or outfits more and more divergent from the norm.
They have to live and believe a certain way or be excluded. They may have to prove their loyalty. Cults are the most extreme group, requiring a complete separation from the member's former life. Members follow extreme ideologies and convince each other of the importance and justification of their beliefs. There have always been fringe groups.