DeFi lending is covered in full in the entry Decentralized Lending Protocol, which explains how pooled lending markets work, how interest rates are set and what risks lenders and borrowers face. This page gives a short definition and explains the different names.
DeFi lending is the practice of lending and borrowing crypto assets through smart contracts on a public blockchain, without a bank, broker or centralized crypto lender in the middle. Lenders deposit tokens into a shared pool and earn interest; borrowers lock up collateral worth more than their loan, an arrangement known as an over-collateralized loan, and pay interest that rises and falls with demand. If the value of a borrower's collateral drops too far, the protocol sells it automatically to repay the debt. Well-known protocols include Aave and Compound. A special feature with no close equivalent in traditional finance is the flash loan, which must be borrowed and repaid within a single transaction.
"DeFi lending" describes the activity, while "decentralized lending protocol" describes the software that provides it. Because the two names refer to the same thing, this site keeps one main entry under the protocol name.