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