Air handlers and furnaces aren't usually found in the same home in Indianapolis. 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 around your house. Some models also have extra heating and cooling components to support the heat pump.
A furnace heats in a different way by blowing warm air into your vents, which send it around your home. Since furnaces depend on combustion chambers to create hot air, they don't have some of the components you'll see in a normal air handler.