A negative pledge is like a promise where someone says they won't do something. In this case, it's when someone who borrows money promises that they won't use their assets (like a house or a car) as collateral for any other loans or debts. It's like saying "I promise to keep my toys in my room and not give them away to anyone else." If the borrower breaks this promise and uses their assets as collateral for another loan, they could get in big trouble with the people they borrowed from before.