Air handlers and furnaces aren't usually found in the same home in Charlotte. If you use a furnace, you probably shouldn’t need to think about an air handler.
Air handlers are frequently used with heat pumps and control airflow across your residence. Some systems also have backup heating and cooling pieces to help the heat pump.
A furnace works differently by sending warm air into your vents, which circulate it around your home. As furnaces have combustion chambers to produce heated air, they don't need some of the pieces you'll see in a normal air handler.