a thesis statement is a sentence, or a couple sentences, that provide a quick overview of the points you are going to talk about later in the speech or essay. EX: Books are a good source of knowledge because they provide facts, widen vocabulary, and increase a person's reading comprehension.
A thesis statement is the statement or subject sentence of the writing itself. Like, if the thesis statement was based on a book or story, you would obviously use examples from the text to support the statement. You basically have to prove and support the statement given. You back the sentence up and go further into detail about it.
Example: I once did a paper called "John Steinbeck- Social critic". Opening paragraph stated what I wanted to show, then I used examples from his writings to prove it. This was the one bit of work in HS of which I was most proud!