Explanatory expository essays ask the writer to explain the reasons or causes that contribute to an event. College students in the social sciences -- such as anthropology, archaeology, business administration or economics -- often need to write in this style, using theories and research to back up the information presented. For instance, an anthropology student might explain the reasons indigenous villagers in Ecuador wear a certain kind of dress or serve certain foods to guests.
An illustrative expository essay communicates to readers a theory or main idea about a subject. The writer composes the paper using descriptive language and examples to illuminate the theory. For example, a science student may write a paper illustrating the how loggers are devastating the ecosystem in the Amazon rainforest. Instead of simply laying down data and facts, the writer illustrates how a breed of insect is going extinct or gives an example of a particular case that supports her theory.
Writing an analytical expository essay means the writer analyzes a certain point of view by making all of the parts of that argument clear. For instance, a write may want to analyze the effects of binge drinking on teenagers. He may analyze the problem by pointing out the resulting brain damage from young people imbibing alcohol and getting drunk and the ways drinking drives a stake between children and their parents and friends who do not drink. The writer looks at the issue or topic with an unbiased view and without a clear opinion. A persuasive essay would sway an audience to agree with his perspective on the issue, but convincing readers to side with you is not the objective of an analytical expository essay.
Descriptive expository essays are often required for science or historical classes. Instead of supplying cut-and-dry facts about the Civil War or a psychological experiment, the writer describes the entire event by including a background and analyzing the event into its sections. For example, if a writer is composing a descriptive expository essay on prisoners of war in Cambodia, she might describe the background information about the conflict and the details of the captures. A descriptive essay not only introduces and describes facts but also synthesizes the information into a useful document.