The document discusses the use of "used to" to talk about past habits or regular activities in the past. It provides examples of using "used to" in affirmative, negative, and question sentences. Key points: - "Used to" is not a tense but a structure used to talk about the past. - In negative sentences, "used to" changes to "use to" when "didn't" is present. - In questions, "use to" is used after "did" but "used to" is used without "did". - Common examples show activities that are no longer done in the present compared to the past.