Decentralised finance, or DeFi for short, is probably the most revolutionary concept in the universe of digital assets presently. But what is it, how does it operate, and why has it been placed at the forefront of the money and banking of tomorrow? In order to understand DeFi, one has to look at the way financial systems operated in the past, how blockchain technology has enabled a new system, and the way stablecoins such as USDC are enabling people to trade the old for the new.