When a writer wants to educate readers on a topic or a concept, they have two similar choices in how to approach the subject. If a writer chooses to present information to the reader in general, an informational essay would be an ideal approach. If, however, the writer wants to educate the reader with facts and evidence that supports a topic or thesis argument, they would choose an expository essay.
The Expository writing definition is to present information to the reader while also sharing concepts and ideas that are backed up by facts and evidence. One of the best ways to think about expository writing is a neutral journalist writing on a particular topic that has multiple points of view. If the journalist presents all the information and evidence in a neutral way without picking a side, then they have written an expository piece.