There are many normative facts: we have reasons to perform certain actions, certain outcomes of actions are better than others, certain people are virtuous whereas others are vicious, and so on. What explains these very different normative facts? As I understand it, constitutivism is an answer to this question. According to constitutivists, normative facts of certain kinds are explained by facts about the constitutive features of something—that is, the features in virtue of which that thing is the kind of thing it is—where the constitutive features might be those of some person, or some action, or some state of affairs, or something else entirely. Constitutivists may disagree about this.