Maturity is pretty straightforward. A bond's maturity is the length of time until the principal must be paid back. So a 10-year bond will earn interest for 10 years from the date it is purchased. At the end of that time period the bond's principal is repaid to the owner of the bond and interest payments cease. A bond's duration, on the other hand, is a more abstract concept often used to measure interest-rate sensitivity. Bond investors often pay attention to interest-rate movements because any movement up or down in rates has the opposite effect for bond prices. That's because an increase in interest rates makes an existing bond (and its now below-market interest rate) worth less while a drop in rates increases the bond's value.