What is it good for?
The systems development life cycle (SDLC), also referred to as the application development life-cycle, is a term used in systems engineering, information systems and software engineering to describe a process for planning, creating, testing, and deploying an information system. The systems development life-cycle concept applies to a range of hardware and software configurations, as a system can be composed of hardware only, software only, or a combination of both."Systems Development Life Cycle" Wikipedia. Wikimedia Foundation 
Research and determine the project's current situation and needs.
Establish the scope of the project, planning, and project methodologies.
Design using the Style Guide and other approved brand identity assets. Technical and functional design decisions are made in this stage.
Coding. Test it and repeat until development sins can be forgiven. Write Documentation.
Deployment runs concurrently with Development.
Repeat - Iterate - Improve