NCDs and Bonds, both are fixed income instruments. However, there are a few differences between NCD and Bonds like-
NCDs are issued by public companies, whereas bonds are issued by government entities, large companies, and financial institutions to raise capital for the business purpose.
Bonds are generally secured, whereas NCDs can be secured and unsecured.
At the time of liquidation, priority to repay the debt is given first to bondholder and second to debenture holders.