Asset backed securities are debt instruments (i.e. a type of bond) secured against specific assets or against specific cash flows.
Asset backed securities may be used to remove assets from the issuer's balance sheet or to manage risk by limiting lenders' recourse other than to the specific assets concerned.
The creation of an asset backed security requires the securitisation of a pool of assets or a series of future cash flows.
In some cases the assets may themselves be backed by other assets belonging to the issuer's borrowers. For example, a bank might finance a large chunk of its mortgage lending with an asset backed security.