Formal teams are created for specific, important purposes and have structured operations to achieve goals within set constraints like budgets and timelines. Examples include job interviewing teams and event planning teams. Informal teams form more casually to improve work processes in less important ways without constraints, like sports teams discussing game tactics. The optimal team size is around five members, large enough for diverse skills and perspectives but small enough for involvement and efficiency. Temporary teams work together just for one project, while permanent teams collaborate continuously as part of an organization. Benefits of teams include setting and monitoring goals, reviewing performance, sharing expertise, fostering innovation, and identifying talents.