Debt securities, also known as liens, are financial instruments that represent a loan between two parties. They are typically issued by corporations or governments to raise capital and are secured by the issuer's assets. The lender is entitled to repayment of the principal plus interest, and the issuer is obligated to make payments on the debt security until it matures. Liens are a form of debt security that gives the lender a legal claim against the issuer's assets in the event of default.