Each person plays a tightly or loosely defined role in the process of collaboration. For instance, to make a movie a writer, director, producer and actors are needed. There may also be a need for a costumer, a cameraman (if the director cannot do it all), an audio engineer, and a film editor if the project is big enough and the schedule tight enough.
Not only individuals collaborate; groups also do it. Large construction projects are usually done by collaborations between corporations, wars are often fought between alliances of countries, and political parties often collaborate in government.