Building on Mises’ pioneering work, this chapter delves into the historical evolution of money, examines various types of money—particularly the distinction between commodity and fiat money—and discusses the concept of economic calculation. Mises emphasizes that money is not a “neutral” medium but a key factor in determining prices through subjective valuations by economic actors. While supporting the quantity theory of money, he criticizes the simplistic interpretation presented by the “equation of exchange.” The chapter also analyzes the redistributive impacts of changes in money supply, known as the “Cantillon Effect,” and investigates purchasing power parity in relation with currency exchange rates.