A debenture is a debt instrument issued primarily by companies to raise funds. Investors lend money for a fixed period, and in return, the issuer pays interest at set intervals and repays the principal at maturity.

Debentures can be secured or unsecured, with repayment largely dependent on the issuer's financial health. While all debentures are debt instruments, not all debt instruments are debentures; they are a specific type within the broader bond universe.