A debenture holder earns fixed interest. A debenture is a type of bond or debt instrument issued by a company or organization to raise capital. When an investor buys a debenture, they are essentially lending money to the issuer. In return, the issuer pays the debenture holder a fixed rate of interest for a specified period of time, usually until the debenture matures. This fixed interest payment is the main source of earnings for a debenture holder.