waterfall-model, as is evident from the name, refers to a systematic approach where one step comes after the other. It cannot go the other way round. The process works like the waterfall effect that flows in one direction, which is from up to down.

In this process the life cycle of the development process is predetermined. All the steps are defined before the start of the project. The approach is predictive, where the team is well aware of the order of each step and therefore works accordingly. It starts from the requirement analysis, the design phase and then proceeds on to the implementation, testing and the maintenance phases.

The waterfall-model can be quite beneficial for those who are quite clear on their requirements.