This document provides an overview of heating, ventilation, and air conditioning (HVAC) systems. It discusses the history and development of HVAC, including early innovations in refrigeration. The core components and functions of HVAC systems are described, such as furnaces, ducts, air conditioners, and heat pumps. Various types of HVAC installations and systems are covered, like central air, zoned heating, and radiant heat. Recent developments in HVAC technology and applications are also summarized along with the advantages and disadvantages of HVAC.