What are generally accepted practices for using segmentation in optimizing digital advertising / paid search landing pages?

What are generally accepted practices for using segmentation in optimizing digital advertising / paid search landing pages? Answers must include: Definition of terminology, Importance of the concept or process, and the Process of how a professional marketer approaches the practice. Please start your answer so it can stand alone as a sentence/paragraph. For example, “SEO keyword analysis is the process of…”