Air handlers and furnaces aren't usually installed side by side in Clearwater. If you rely on a furnace, you likely don't need to think about an air handler.
Air handlers are frequently used with heat pumps and deliver airflow across your house. Some units also provide extra heating and cooling components to help the heat pump.
A furnace runs in a different way by blowing warm air into your vents, which circulate it around your home. As furnaces depend on combustion chambers to produce heated air, they don't use some of the pieces you'll spot in a regular air handler.