Groups can be formal or informal. Formal groups are defined by an organization's structure, while informal groups emerge to fulfill social or interest-related needs. There are several reasons why people join groups, including security, status, and goal achievement. Groups go through forming, storming, norming, performing, and adjourning stages of development. Effective teams are composed of competent, committed members who work collaboratively to achieve well-understood, accepted goals. They tend to have an atmosphere of respect, trust, and informal communication where members freely share ideas and resolve disagreements constructively.