An expository essay "exposes" the reader to a new topic; it informs the reader with details, descriptions, or explanations of a subject. If you are writing an expository essay, your thesis statement should explain to the reader what she will learn in your essay.
What is the thesis for an expository essay?
An expository thesis statement states the topic of your paper and lists the key aspects of your topic that will be discussed in the paper.
Is there a thesis in an explanatory essay?
Thesis Statement
As the explanatory essay is tailored to explain or acquaint your readers with something, the goal of the explanatory thesis is to tell readers what it is you are going to explain and what aspects of the topic will be considered.