Can anyone explain this concept to me in simple terms i am not able to grasp this concept.
Options have value. Option-adjusted removes the value of the option from the price.
A bond with an embedded call option will be priced at a discount (higher coupon) because you are being compensated for the risk that the bond will be called away from you before all of the interest can be paid to you. An embedded put option will be priced at a premium because you have the luxury of selling the debt back to the issuer if the rate environment moves against you.