A Mortgage-Backed Securities (MBS) is an investment that resembles a bond and is composed of a collection of mortgages that have been acquired from the banks who issued them. Periodic payments akin to bond coupon payments are made to MBS investors.The MBS market is a market for securities backed by mortgages, home loans and real estate.Mortgage-backed securities are one of the most popular investments in the world. They are also called mortgage pools or collateralized mortgage obligations (CMOs).