The document discusses software development life cycles (SDLC). It describes the typical stages of an SDLC including feasibility study, requirements analysis, system design, development, testing, implementation, and maintenance. Several SDLC models are mentioned, including waterfall, spiral, iterative, prototyping, and RAD (rapid application development). The waterfall model is described as having distinct sequential stages with no overlap between phases. Prototyping and RAD methodologies are also explained in further detail.