This document provides an overview of health care for the homeless, including: 1) It discusses the realities of homelessness in the US, including estimates of the number of people experiencing homelessness on a given night or over a year. 2) It outlines some of the key health challenges faced by homeless populations, such as higher rates of medical and behavioral health conditions, and barriers to accessing continuous health care. 3) It also summarizes characteristics of different homeless subpopulations like families, youth, and those with severe mental illness or substance use disorders.