What Is Compare and Contrast Expository Writing?
The purpose of compare and contrast writing is to identify two or more things that are related, and explain the ways they are the same (compare) and the ways they are different (contrast).   The writer accomplishes this by identifying two or more things they wish to compare and contrast, then by writing a clear thesis statement about them, and by supporting their thesis with relevant evidence. 

Compare and Contrast Essays Are One Type of Expository Writing
The purpose of expository writing is to explain information. There are different types of expository writing, and compare and contrast writing is just one of those types. The purpose of an essay will determine which type of writing (from those listed below) you will use and how you will organize the information. The 2012 School-Wide Writing Assignment focuses only on compare and contrast expository writing.  

Informative

Informative expository writing provides information about a topic. There are two types of informative writing:  
1. Descriptive informative writing describes the topic by providing examples, characteristics, and features. 
2. Sequential informative writing lists the items or events in numerical or chronological order.   

How-To

“How-to” expository writing explains how to do something.  “How to” writing has a time order to it.

Compare-Contrast

In compare-contrast expository writing, two subjects are shown how they are similar and how they are different.


Cause-Effect

In cause-effect expository writing, the cause is given as part of the thesis, and the effects are discussed.

Problem-Solution

In problem-solution expository writing, the problem is stated as part of the thesis, and the solutions are discussed.    

Compare and Contrast Expository Essays Are Multi-Paragraph
--There is an attention-getting introduction that presents the topic and the writer's position (thesis) in a compelling way. The introduction might also present the writer's main ideas in support of their position (thesis) in order to "frame" the scope and breadth of the concepts presented in the body paragraphs.
--There are body paragraphs that present the compare and contrast evidence in support of the writer's position (thesis). The main ideas are supported with examples/details/facts that are relevant and interesting, and that anticipate the reader's questions.
--There must be relevance and logic between the writer's position (thesis), main ideas, and the examples/details/facts in support of the main ideas.
--The concluding paragraph is the writer's last chance to re-state their position and re-focus the reader as to the main ideas given in support of the ways the things being considered are alike and the ways they are different. It should be as compelling as the introduction paragraph.

When Is Compare and Contrast Writing Used?
Evaluate: We use compare and contrast thinking everyday when we compare and contrast related things and evaluate them to help us make choices and decisions. We also use compare and contrast thinking when looking at the features of something new to something already in existence in order to help us evaluate which one is best for our situation. When we write a compare and contrast essay with accurate information, then we are giving the reader the information they need to make an accurate evaluation for their situation.
Inform: We also use compare and contrast writing to give information about two or more things that are related in some way. The information is not being presented with the purpose of helping someone make an evaluation or decision, but it is presented to provide information to the reader about two or more things that are related in some way by showing what they have in common (compare) and how they are different (contrast).

Types of Compare and Contrast Writing Include:
Exams
Business Reports
Academic Papers
Everyday Workplace Communications
Memos