Waterfall development is a linear and sequential approach to product or software development, consisting of distinct phases: requirements gathering, system design, implementation, testing, deployment, and maintenance. Each phase must be completed before moving to the next, with little flexibility to revisit earlier stages. This model assumes that all requirements can be fully understood and defined at the start, which can be limiting in projects where requirements may change or evolve. [[agile development|Agile development]] is frequently favored over waterfall for its flexibility and iterative approach, allowing teams to adapt to changing requirements and customer feedback throughout the project lifecycle.