Air handlers and furnaces aren't usually installed side by side in Gainesville. If you have a furnace, you most likely don't need to think about an air handler.
Air handlers are usually linked with heat pumps and deliver airflow throughout your residence. Some units also provide extra heating and cooling parts to help the heat pump.
A furnace runs differently by pushing warm air into your vents, which circulate it around your house. Because furnaces have combustion chambers to produce warmth, they don't use some of the parts you'll spot in a regular air handler.