There are also smaller, friendlier groups where everyone is treated equally. These are the groups you should join. DO NOT join groups with a negative attitude, or one centered on your looks. It's very important to look good, but personality also matters. Instead of joining a group, a good idea is to start your own.
Cliques are friendship groups made of people who like each other's company.
They develop unwritten rules that restrict freedom of members. Amid all these problems, the reason cliques remain popular is because many people are very happy to be accepted into a clique, especially if it is popular. She has just been accepted into a clique made of the really popular girls in her school. They had nice, expensive clothes, were pretty, and popular with the boys. However, she felt she could not be herself with the group.