The heat is provided by the furnace and the fan runs throughout the year to circulate air for both the heat and the A/C. There is an evaporation coil that is the indoor system component working with your cooling unit, which is placed outdoors. The air ducts carry both heated and cooled air throughout the home while the thermostat is your control for the system.
The U. S. regulatory agencies require all new air conditioning systems to have a SEER rating (Seasonal Energy Efficiency Ratio) of 13.0 or better. We have some A/C systems with SEERs as high as 21. They also require that oil-fueled or gas furnace have an AFUE (Annual Fuel Utilization Efficiency) rating to demonstrate how much of the fuel consumed is actually used in producing heat and how much is wasted. With both of these ratings the higher the number, the greater the energy efficiency and energy bills savings you will receive with the system. We even have some furnaces with AFUEs greater than 98.