Peer pressure is a force that happens within a group of people. It often happens to children during puberty. The group defines some social values. For somebody to stay "cool" in that group, they feel as if they have to act like other people in that group. Social pressure (and wanting to be accepted or in favor inside the group) leads people to do things they would not do otherwise. For example, it can make a person to smoke cigarettes or marijuana, to drink alcohol, commit crimes, and/or many other things.