Bonds are units of corporate debt that are issued by companies and traded as securities. They traditionally pay a fixed rate of interest and the price is inversely related to interest rates, so prices fall when rates rise. Bonds have a face value paid back at maturity. Key characteristics include the coupon rate, coupon dates, maturity date, and issue price. Common types are zero coupon, convertible, fixed-rate, floating-rate, perpetual, inflation-linked, callable, and puttable bonds. Bond prices are determined by interest rates and yield-to-maturity calculations.