It is a traditional software development methodology. In this customer may not see the end product until it completes. It is relatively linear sequential design approch. Requirements, design, implementation, verification, maintence are the different phases of waterfall model.
Agile Scrum Model
It is particular approch to project management that is utilized in software development it is based on iterative development where requirements evolve through collaboration between self-organizing cross-functional teams. It quality of deliverables and cope better with change.
The main motive of DevOps is to strongly advocate automation and monitoring at all phases of software development life cycles. Using DevOps we can achive countinous development, countinous testing, countinous integration and countinous monitoring.