Groups are defined as two or more individuals interacting and interdependent to achieve objectives. There are two types of groups: formal groups defined by organizational structure and informal groups that form naturally. The four types of groups are command, task, interest, and friendship groups. People join groups for status, self-esteem, affiliation, achievement of goals, power, and security. Groups generally pass through five stages of development: forming, storming, norming, performing, and adjourning.