This document discusses the waterfall model of software development. It provides: 1) A brief history of the waterfall model, noting it was the first SDLC model described in 1970 by Winston Royce. 2) An overview of the waterfall model, including that it is the oldest and most basic sequential model with distinct phases from requirements to maintenance. 3) A description of the five phases of the waterfall model: requirements gathering, design, implementation, testing, and maintenance. Each phase feeds into the next and must be completed before starting the next.