This document provides an overview of mortgage markets and mortgage-backed securities. It defines different types of mortgages like home mortgages, commercial mortgages, and adjustable-rate mortgages. It describes how mortgages are securitized into mortgage-backed securities and the roles of government agencies like Fannie Mae, Freddie Mac, and Ginnie Mae in the secondary mortgage market. It also discusses trends in subprime lending and the financial crisis.