Traditional scientific and other types of informational articles begin with an introductory paragraph that summarizes the piece. In scientific writing, it's cal

Traditional scientific and other types of informational articles begin with an introductory paragraph that summarizes the piece. In scientific writing, it's called an "abstract". In general nonfiction exposition, it's a principle of good organization: introduction, body, and conclusion. Of course it's not "required" to provide an abstract or explanatory subtitle at the top; it's just good practice.