A thesis statement is the most important few sentences you will write in a thesis, research paper or any other essay that adheres to APA (American Psychological Association) format.
In an expository essay, you don't need to develop an argument or prove anything; you only need to understand your topic and present it in a logical manner.
A good thesis statement in an expository essay always leaves the reader wanting more details.
A successful thesis statement is one that is made up of one or two sentences clearly laying out your central idea and expressing an informed, reasoned answer to your research question.
Usually, the thesis statement will appear at the end of the first paragraph of your paper.