Waterfall Model

The Waterfall Model is a traditional, linear software development methodology where the project is broken down into distinct, sequential phases. Each phase must be fully completed and approved before the next phase can begin, much like a waterfall flowing in one direction. This rigid, sequential approach makes it difficult to go back to a previous phase once it's been completed.

Example: A team uses the Waterfall Model to build an application with a login feature. They would first spend weeks or months completing the Requirements phase, meticulously documenting every detail of the login process. Once the requirements are finalized and signed off, they move on to the Design phase. After the design is complete, they proceed with Development, and only after all the code is written do they hand the entire application over to the testing team. There's no testing of the login feature until the development of all other features is complete.