A credit line you can borrow against repeatedly up to a limit, like a credit card.
Revolving credit lets you borrow, repay, and borrow again up to a set limit, with no fixed payoff date. Credit cards and home equity lines of credit are common examples. Unpaid balances accrue interest and the way you use revolving credit heavily affects your credit utilization and score.
A credit card is revolving credit; a car loan with fixed payments is not.