Unlike the traditional waterfall methodology where every task or project phase is sequential, Scrum prescribes the notion of iteration. At a high level, with Scrum, a project is broken up into a number of iterations called sprints. Each sprint is usually one or two weeks long; the project team completes a portion of the overall project, and the project is completed when all the sprints are finished. With this approach, the project team is able to do the following:
Continuously deliver with each sprint, so feedback can be gathered early
Accommodate changes during the project life cycle
Identify issues early on rather than at the very end, which is costly
Continuously improve the process with retrospective meetings at the end of each sprint