When someone invests in bonds, they are assured of a fixed rate of interest, irrespective of the market conditions. This rate of interest or yield is called the coupon rate.
The coupon rate is calculated on the face or par value of the bond.

For example, if you purchased a 10-year – Rs 3000 bond with a coupon rate of 10%, then you will receive Rs. 300 (i.e. 10% of 3000) every year for the duration of 10 years.