Groups serve important functions for organizations and individuals. There are formal and informal groups, as well as groups that form based on tasks, interests, command structures and friendships. People join groups for security, status, self-esteem and other reasons. Groups develop through forming, storming, norming, performing, and adjourning stages. They establish roles, norms, status hierarchies and processes for decision-making. Group size, composition and cohesiveness also impact its functions.