Air handlers and furnaces aren't usually installed in the same home in Fort Worth. If you have a furnace, you likely won’t need to think about an air handler.
Air handlers are usually used with heat pumps and manage airflow around your home. Some models also provide extra heating and cooling pieces to support the heat pump.
A furnace works in a different manner by blowing hot air into your vents, which send it across your residence. Since furnaces depend on combustion chambers to make warmth, they don't use some of the pieces you'll find in a standard air handler.