In an essay or research paper, a thesis statement is a statement at the start or the end of an introduction that shows the reader the argument of the essay. A thesis statement gives concise information about what the whole essay is about, including the topic of the paper. It is usually just one sentence but it may have more than one sentence. The thesis statement is explained further using body paragraphs. Thesis statements are not obscure, because obscurity happens when a "writer is himself not quite sure of his meaning. He has a vague impression of what he wants to say, but has not, either from lack of mental power or from laziness, exactly formulated it in his mind, and it is natural enough that he should not find a precise expression for a confused idea.” (W. Somerset Maugham). Clarity and unity of a thought in an essay flows from a good thesis statement. Rubrics of a good essay involve good sentence development and formation acceptable to grammatical standards and relevant word choices organized in forms of phrases, clauses and sentences.
The thesis statement is developed, supported, and explained in the course of the paper by means of examples and evidence. Thesis statements help organize and develop the body of the writing piece. They let readers know, what the writer's statement is and what it is aiming to prove. A thesis statement does not necessarily forecast organization of an essay which can be more complex than its purpose.
The thesis statement will reflect the kind of paper being written. There are three kinds of papers: analytical, expository, and argumentative. The structure of a thesis statement depends upon the nature of controlling essay type. In simple terms, first a thesis statement will have a main topic sentence formed from questioning the topic, then the writer's statement regarding the topic sentence, and finally ends with the specific supporting points detailing the writer's statement for justifying its relation with the topic sentence. In general, it should have a supportable opinion (specific/focused) and clear intent for the essay.