The secondary mortgage market is the market for the sale of securities or bonds collateralized by the value of mortgage loans. A mortgage lender, commercial banks, or specialized firm will group together many loans (from the "primary mortgage market") and sell grouped loans known as collateralized mortgage obligations (CMOs) or mortgage-backed securities (MBS) to investors such as pension funds, insurance companies and hedge funds. Mortgage-backed securities were often combined into collateralized debt obligations (CDOs), which may include other types of debt obligations such as corporate loans.