Investing in bonds should be thought of as an I.O.U between the investor of said bond and the issuer. In other words, you're loaning the issuer money now, for some sort of return later. Bonds are issued by companies and institutions to fund projects and operations. That means if you own a bond, you own a debt. Bond investors should make sure of the end date when the principal of the loan is due to be paid, and the terms under which payments will be made by the borrower.