Truth depends on reality. When something is true, its truth depends upon the world. Its truth is not some brute, inexplicable feature of reality. Truths are true in virtue of reality, and not vice versa. These ideas are the source of the philosophical enterprise known as truthmaker theory. Truthmaker theorists, accordingly, are philosophers who explore the domain of metaphysics by using the tools of truthmaker theory. Explaining what those tools are, and how they are best used, are the main goals of this monograph. The goal of this introduction is to defend the claim that truthmakers are worth caring about, and to identify some of the core motivations that drive the project. It shows how truthmaking ideas are already at work in many philosophical discussions and arguments.