A new way of providing financial services to the masses, minus the middleman in many cases. Think of traditional financial services like money exchange and transfers, savings and lending, but now they're online and digital, global and easily transferrable. They're also programmable, allowing them to be interconnected to other services via different protocols, all existing on the blockchain.
Example
“Using a DeFi lending protocol like Aave, a user deposited ETH as collateral and borrowed USDC without needing a bank or credit check.”