All groups form their own unwritten norms that determine what behavior is accepted. Rules are formally established by management or by the group itself. Norms are not developed by management or explicitly agreed to by a group; they develop as members interact. Norms are expectations about behavior that are shared by members of a group.
Norms develop spontaneously as the members of a group interact and compare themselves to the other members. If a group member does not follow a norm, the other members try to enforce compliance—in other words, peer pressure. As we have all faced group pressure, we can understand how it is a powerful influence over our behavior. Be aware that we tend to adjust our behaviors to try to match that of our team norms.