The answer to 'types of HVAC system' is that there are several common types of HVAC (heating, ventilation, and air conditioning) systems used in homes. The most common types are central air conditioning systems, heat pumps, furnaces, and boilers.
Central air conditioning systems use an outdoor unit to cool the air, which is then distributed through ductwork to vents throughout the home. Heat pumps are similar but can also provide heating by reversing the refrigeration cycle. Furnaces use natural gas, propane, or electricity to heat the air, which is then distributed through ductwork. Boilers use hot water or steam to heat the home, often through radiators or radiant floor heating.