As health care and public health continue to evolve, the field of Health Information Systems (HIS) has introduced a complicated set of new, emerging, competing, and synergistic technologies and services. This guide unravels the mysteries of HIS by breaking these technologies down to their component parts and providing a clear and reader-friendly account of the concepts involved. Topics include an HIS overview, systems and management, health informatics, data and analytics, research and policy as it relates to public health, and the future direction of HIS.