This document discusses the use of "used to" and "would" when talking about past habitual actions and states. It explains that "used to" is used to talk about past states or repeated actions that no longer happen, while "would" can also be used for repeated past actions. Only "used to" can be used for past states. While both "would" and "used to" can be used in the affirmative, only "used to" can be used in the negative without changing the meaning when referring to past habitual actions or states.