This document provides an overview of the mortgage market in the United States. It describes the primary mortgage market where loans are originated by lenders like banks and then sold to investors. It also details the secondary mortgage market where government agencies and private institutions facilitate the buying and selling of existing mortgages through securities like mortgage-backed bonds and pass-throughs. The document outlines the origination process and underwriting criteria lenders use like payment-to-income ratios when providing mortgages to borrowers.