This document discusses the use of "have to" and "don't have to" to express obligation and lack of obligation. "Have to" is used to talk about things that are necessary or required, like obligations. "Don't have to" expresses when something is not necessary or required to do. Examples are provided of affirmative and negative sentences using these phrases. The document also provides practice ordering sentences and filling in blanks with "have to", "doesn't have to", etc. to talk about different obligations.