Coupon bonds like zero coupon bonds offer a discount on bonds. These bonds pay a discount bond yield to maturity.
They do not pay the yield until the bond matures. That is why these bonds are called zero coupon because the interest is paid at maturity.
A bond discount yield occurs when the actual yield of the bond is lower than the market rate of the bond. Premium and discount bonds are different. Premium bonds are sold at a higher value, while discount bonds are issued at a discount.