This chapter defines the key terms used in this primer. It summarizes various concepts that have been used to analyze constitutions (such as that of the social contract, a principal–agent relationship, and so forth). It discusses some of the methodological challenges that constitutional economics faces, presents some of the tools that are used to gain insights, and discusses some of the most relevant outcome variables used in later chapters. These include fiscal variables (such as government revenue, government spending, and budget deficits), governance variables such as corruption and government effectiveness, as well as traditional macroeconomic variables such as total factor productivity.