What is a waterfall model?

In Waterfall Model, There are various phases which need to be followed from sequentially one phase to the next. Waterfall Model is a traditional project management procedure in which sequential development process is followed. Also in this model, development actually moves in downward direction. It also consists of few phases like initiation, analysis, design, build, test, and maintenance. Besides, agile model is preferred over waterfall model now-a-days, waterfall model is always there in project management terms cheat sheet.