A bond is really just an investment. When someone, an investor, buys a bond from a financial institution, he or she pays a fixed amount of money for the bond, and after a set amount of time, is paid his or her investment back, with a certain amount of interest. A bond is not like a stock though. If an investor sells the bond before it matures, it's best if he or she sells it for a higher value to a lender (such as a financial institution) that needs it more.