Imagine two countries where the average income is the same. In one, a few families live in huge palaces while almost everyone else struggles to get by. In the other, most people enjoy a comfortable middle‑class life. Which country is truly better off? That question captures why we study inequality. We care not only about the size of the economic pie, but also how it is divided. In this chapter, you will learn the tools that economists use to measure inequality. We will look at long‑run patterns like the Kuznets curve and the recent jump in top incomes. And we will unpack the many ways that inequality can either help or hurt economic growth.