Groups don't become teams simply because that's what someone calls them. Many organizations have a "management team" but it doesn't mean that the members behave like a team or demonstrate teamwork. Most commonly, management teams meet periodically to provide each other with updates rather than to do real work together.
Teams differ fundamentally from groups because they require mutual accountability. Groups can be successful based on the contribution of individuals whereas a team requires people to work together to achieve a common goal. Jon Katzenbach and Douglas Smith capture this distinction in their definition of a team as “a small number of people with complementary skills who are committed to a common purpose, set of performance goals, and approach for which they hold themselves mutually accountable.”
Teams aren't always the best approach and groups or individuals can sometimes be more effective. If a task does not require joint work products, a group may be more effective. If a task requires people with interdependent skills to work across organizational silos then a team is most likely the best approach.
