What does HVAC stand for?
Heat pumps (electric), furnaces (gas or electric), one system package units (gas or electric), dual fuel systems (will access either gas or electricity depending on the outside temperatures.
Vents, ductwork, and dampers to control air flow.
AC: Air Conditioning
Heat pumps, and one system package units both heat and cool your home through the same system. Central air conditioning systems work with dual fuel systems and your furnace.