Air handlers and furnaces aren't often installed side by side in Richmond. If you use a furnace, you probably don't need to think about an air handler.
Air handlers are typically used with heat pumps and deliver airflow throughout your home. Some models also provide backup heating and cooling components to assist the heat pump.
A furnace heats in a different manner by sending hot air into your vents, which send it across your residence. As furnaces depend on combustion chambers to make warmth, they don't use some of the parts you'll find in a regular air handler.