AC stands for air conditioning, which is a system used to cool and dehumidify air in a space. It works by circulating air through a refrigerant-filled evaporator coil, which absorbs heat from the air and transfers it to the outside. HVAC stands for heating, ventilation, and air conditioning. It is a system that provides heating, cooling, and ventilation to a space. It works by circulating air through a network of ducts, which are connected to a furnace, air conditioner, and other components. HVAC systems are designed to maintain a comfortable indoor environment by controlling temperature, humidity, and air quality.