Abstract: This is the first chapter of the book Corporations in 100 Pages (2020), authored by Holger Spamann, Scott Hirst, and Gabriel Rauterberg. The book is an introduction to corporate law for students and anyone else interested in the foundations of corporate law. The book provides an accessible, self-contained presentation of the field’s essentials: what corporations are, how they are governed, their interactions with their investors, and other stakeholders, major transactions (M&A), and parallels with other legal entities, including partnerships. Optional background chapters cover the investor ecosystem, contemporary corporate governance, and corporate finance. The book’s exposition of doctrine and policy is nuanced and sophisticated, yet short and simple enough for a quick read. Chapter 1, “Corporations & Corporate Law,” introduces the book by addressing two questions: What are corporations? And what is corporate law? The chapter discusses the corporation as formally an abstraction to which the law assigns right and duties. Its extraordinary usefulness lies in how it allows large groups of people to organize relationships involving multiple assets, such as by pooling funds, transferring them to the corporation, and then allowing the corporation to serve as a single contracting interface with third parties. The chapter discusses how corporate law, as the subject is taught in law schools and discussed in practice, consists of the body of rules that govern the relationships among a corporation’s shareholders, its board of directors, and its managers; the relationships within each group; and the powers of each group to affect the corporation’s affairs. Corporate law is thus only a small subset of the far larger set of laws governing corporations, which includes “antitrust law,” “consumer law,” “environmental law,” and far more. Corporate law remains largely a matter of state statutory and common law, but also turns decisively on the corporation’s governing legal instruments, like the charter and bylaws, and contracts amongst its shareholders. Securities law also affects how corporations finance themselves. The chapter ends by providing examples of corporations, such as a small private corporation and a large public one, which illustrate the important legal features of the corporate form.