What are generally understood ways in which landing pages work in conjunction with digital advertising / paid search campaigns?

What are generally understood ways in which landing pages work in conjunction with digital advertising / paid search campaigns? 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…”