Cryptocurrencies have long been heralded as the future of finance, but it wasn’t until 2020 that it finally caught on to an old idea: making money with money. In the crypto world, decentralized finance (or DeFi) encompasses a wide array of blockchain-based applications intended to enhance cryptocurrency holders’ returns without relying on intermediaries — to earn the kind of passive returns an investor might get from a savings account, a Treasury bill, or an Apple Inc. bond.