Final answer:
Expository essays are written as if the writer is explaining or clarifying a topic to the reader, providing categories or reasons that support the clarification of the paper.
Step-by-step explanation:
The main aim of an expository essay is to provide an effective explanation of a topic. While a descriptive essay strives to describe a subject or a narrative essay seeks to show personal growth, an expository essay tries to explain a topic or situation. Thus, expository essays are written as if the writer is explaining or clarifying a topic to the reader. Since an expository essay is trying to clarify a topic, it is important that it provides the categories or reasons that support the clarification of the paper. Moreover, these categories and reasons also provide the framework for the organization of the paper.