The adjective collaborative describes something accomplished by working together with others. With a collaborative effort, a big job can be completed in very little time.
When you collaborate, you cooperate, or join forces, with other people — working on a project, brainstorming ideas, even assigning responsibility for who will do what. So something that has these qualities is collaborative. From playing in a band to making a movie, feeding the students at a school to building a house, when you work toward a shared goal, it's collaborative.