The peer group is critical to an adolescent's healthy emotional development and it doesn't take an Einstein to realize that teenagers prefer each other's company to that of their parents. Although this is a normal and expected part of growing up, parents can still feel a sense of rejection and loss as the child who used to love to bake cookies with Mom or toss around a baseball with Dad now prefers to spend every free minute with friends.
Friends provide a sense of security.
Feeling part of a group gives teens the confidence to move from childlike dependence upon parents to a more interdependent relationship, an important task of adolescence. Belonging to a group of friends also helps teens as they're developing their, as yet, fragile sense of identity. Feeling a part of a group, be it the jocks, the goths, or the punks, allows them to feel like they are on their way to answering some of these unsettling questions, at least in part. Friends are also important as models of new skills and social behaviors, some good and some not so good. The peer group gives this powerful feedback by their words and actions and so either encourages or discourages certain behaviors and attitudes.