The thesis statement in an essay explains to the reader what the main point or idea of the essay is. The thesis is generally only one or two sentences.
Thesis statements are found in the first paragraph of the essay, usually the last sentence. Thesis statements are intended to be brief and to the point. This allows the reader to learn what is discussed specifically in the essay.
It is not uncommon for the topic of the essay to change or evolve with the writing of the essay. This is why most thesis statements undergo several rewrites before the final version is selected.