Expository writing is a type of writing that is used to explain, describe, give information, or to inform the reader. Authors use this to describe their topic by going more in depth on information provided in their essay. Using an expository format you provide several ways to organize your story. The purpose of an expository essay is to describe information on another level leading the reader to a more advanced and in depth story. To write a effective expository essay, it should contain a main idea, supporting details, and a conclusion. This type of writing is important because it allows the author to show his knowledge by going in depth and providing vivid and descriptive details to each feature of his story.