Lending
DeFi allows any individual to take out or supply a loan without approval from a third party. The large majority of lending products use popular cryptocurrencies such as Ether ($ETH) to secure outstanding loans through over-collateralization. Thanks to the advent of smart contracts, maintenance margins, and interest rates can be programmed directly into a borrowing agreement with liquidations happening automatically should an account balance fall below a specified collateral ratio.
To date, lending has been the leading DeFi use-case.[1]