In the context of digital advertising / paid search, what are commonly accepted practices for choosing an ad serving option based on business goals?

In the context of digital advertising / paid search, what are commonly accepted practices for choosing an ad serving option based on business goals? 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…”