HVAC stands for Heating, Ventilation, and Air Conditioning, and it is a system that is used to regulate the temperature, humidity, and air quality of a space. HVAC systems can be powered by either a furnace or a heat pump. A furnace is a device that burns fuel to generate heat, while a heat pump is an electrically powered device that transfers heat from one area to another. Both systems are used to heat and cool a space, but the type of system used depends on the climate, the size of the space, and the budget.