Air handlers and furnaces aren't typically used in the same home in Tulsa. If you rely on a furnace, you most likely don't need to consider an air handler.
Air handlers are often linked with heat pumps and manage airflow across your residence. Some systems also offer secondary heating and cooling pieces to help the heat pump.
A furnace runs in a different manner by blowing warm air into your vents, which move it around your residence. Since furnaces use combustion chambers to produce warmth, they don't need some of the parts you'll spot in a standard air handler.