During the teenage years, children begin to define who they want to become as an adult.
One step in this process is to become involved with a reference group. Since these groups are already established, young people strive to find the group in which they're most accepted. The results of this process is the development of a number of cliques in high schools.
After high school, young adults go through a phase of self-discovery. At this age, young people are also very interested in getting to know themselves and their circle of friends very deeply. Thus you get: late night chats, road trips, and self-discovery in study-abroad programs, and other stuff like that.
***I wrote a pretty good paper about this two years ago. I should find it and read it.
In the final analysis, being a teenager is a pain. Find your comfort zone and stay there. Also, pay attention to academics. A good education is the most important thing that you can have in order to help ensure upward mobility in life.