The definition of HVAC stands for Heating, Ventilation, and Air Conditioning. It is a system that is used to provide thermal comfort and indoor air quality. HVAC systems are composed of several components that work together to provide a comfortable indoor environment. The components include a furnace, air conditioner, air handler, evaporator coil, and ductwork. The furnace is responsible for providing heat, while the air conditioner cools the air. The air handler is responsible for circulating the air throughout the home. The evaporator coil is responsible for removing moisture from the air. Finally, the ductwork is responsible for distributing the air throughout the home. HVAC systems are used in both residential and commercial settings, and are essential for providing a comfortable indoor environment.