Air handlers and furnaces aren't often found in the same home in Atlanta. If you rely on a furnace, you probably shouldn’t need to think about an air handler.
Air handlers are often paired with heat pumps and deliver airflow across your residence. Some models also have extra heating and cooling components to help the heat pump.
A furnace runs differently by blowing heated air into your vents, which move it around your house. Because furnaces use combustion chambers to make heat, they don't have some of the components you'll see in a standard air handler.