Part I: Why Payments Exist (And Why They're Hard)
Before we talk about cards, networks, or APIs, we need to understand what money actually is and how the first payment systems emerged. This Part builds the foundation in three layers: what money really is (Chapter 1), how the first payment networks formed around trusted institutions (Chapter 2), and how clearing and settlement grew into the financial plumbing that still carries every cross-border payment today (Chapter 3).