Air handlers and furnaces aren't often found together in Columbus. If you use a furnace, you probably won’t need to think about an air handler.
Air handlers are often used with heat pumps and deliver airflow across your home. Some models also offer backup heating and cooling pieces to help the heat pump.
A furnace works in a different way by sending warm air into your vents, which circulate it around your house. As furnaces have combustion chambers to make heat, they don't need some of the pieces you'll find in a standard air handler.