A mortgage-backed security (MBS) is an ABS where the specific assets behind the security are mortgages. A collateralised debt obligation (CDO) is an ABS where the specific assets behind the security are bonds, often a pool of MBS. A covered bond is a one where the bond issuer is obliged always ...

A collateralized debt obligation (CDO) is a complex structured finance product that is backed by a pool of loans and other assets and sold to institutional investors. Essentialy, they are bundled debt resold to to investors.

MBS, as their name implies, are made up of mortgages—home loans bought from the banks that issued them. In contrast, CDOs are much broader: They may contain corporate loans, auto loans, home equity loans, credit card receivables, royalties, leases, and, yes, mortgages.

A CMO is a type of MBS, but CMOs are different because they are broken up into tranches, and the way the investors who own them get paid is different than with a traditional MBS.