Mortgage backed securities (MBS) come in two main varieties; commercial mortgage backed securities (CMBS) and residential mortgage backed securities (RMBS). While CMBS are backed by large commercial loans, referred to as CMBS or conduit loans, RMBS are backed by residential mortgages, generally for single family homes. Residential mortgage backed securities may be backed by a variety of different kinds of residential loan products, such as home equity loans, as well as FHA loans.
A CMBS, or Commercial Mortgage Backed Security, consists of a group of commercial property loans that have been pooled together and securitized, in order to be sold to investors. These securities are broken into various layers, or tranches, each of which has a different level of credit quality, carries a different amount of risk, and offers a different return for investors.