In the Waterfall model, each phase of the development process must be completed before the next phase begins. This model is structured around a strict order of stages, often including requirements definition, system and software design, implementation, testing, deployment, and maintenance. This approach emphasizes thorough documentation and clear milestones, making it easier for teams to manage time and resources at each step of the project. However, the inflexibility of the model can lead to challenges if requirements change during the project lifecycle.