What do you understand by the term debentures?

A debenture is a debt security issued by a company or government. In the UK it means a corporate bond, where the issuer is the company or government and interest payments are made in periodic instalments. A debenture that is "on its face" appears to have certain characteristics: It carries no premium (the purchase price must be paid up front), it has only one maturity date, and most importantly, there may be restrictions on transferability – i.e., you can't sell your rights to this debt security to someone else without permission from the issuer of the claim.