Linear sequential model for software engineering is also known as waterfall model. The linear sequential model suggests a systematic sequential approach to software development that begins at the system level and progresses through analysis, design, coding, testing, and support.
Waterfall is also referred to as a linear-sequential life cycle model. It is very simple to understand and use. In a waterfall model, each phase must be completed before the next phase can begin and there is no overlapping in the phases. The waterfall model is the earliest SDLC approach that was used for software development.