HVAC stands for Heating, Ventilation, and Air Conditioning. Examples of HVAC systems include furnaces, air conditioners, heat pumps, boilers, and air handlers. Furnaces are used to heat air and distribute it throughout a building, while air conditioners cool air and circulate it. Heat pumps are used to both heat and cool air, while boilers are used to heat water and circulate it through radiators or radiant floor systems. Air handlers are used to circulate air throughout a building, and are often used in conjunction with other HVAC systems.