This chapter aims to provide a rounded conception of what law is. It discusses the theoretical conceptualizations of law and the principles of the English legal system. It explains the distinction among different types of law including the distinction between criminal law and civil law, and the differences between public law and private law. The chapter also introduces several sources of law, including statute law, case law, and equity. This chapter provides the different meanings of the terms common law and civil law and clarifies that the English legal system refers to the legal system of England and Wales. The devolution of law-making powers is also discussed.