Lending is the process of depositing (i.e. supplying) tokens in a lending network. In exchange for providing liquidity to the lending protocol, users receive interest on the tokens they have deposited. The interest that lenders receive comes from other users who are paying interest to borrow tokens.
Lenders are able to withdraw their tokens at any time (as long as they aren't being used as collateral to borrow tokens, and not all of the tokens are being borrowed).
Borrowing is the act of taking a loan from a lending protocol. Contrary to lending, which has users supplying tokens to a pool of assets, borrowing is the act of taking tokens out of the pool of assets. L-Fi lending requires users to lend tokens before borrowing, also known as over-collateralization.