This chapter discusses the nature and substance of public policies—one of the key outputs of the policy process. This chapter begins with a broad definition of the term “policy.” It then turns to a discussion of the different ways to categorize policies into different policy types. The effort to place policies into types has consumed a considerable amount of time and effort among political scientists, and for good reason. Political scientists seek to create policy typologies because we suspect, on the basis of intuition and experience, that some policies will involve more groups in the formation and enactment of those policies, will see more conflict before and after enactment, and will be more visible than other types of policies. If we could develop sound policy typologies, we could predict what sort of politics will accompany particular kinds of policies—that is, for a given proposal about what government should do or should not do, we should be able to predict who will participate and what the nature of conflict will be. There is no final word on how best to categorize policies, so when reading this chapter, it is important not to pigeonhole or force fit policies into different categories; instead, a key goal is to consider the strengths and weaknesses of each typology in telling us something meaningful about the way policy is made and what its results likely will be.