Air handlers and furnaces aren't typically used together in Voorhees. If you use a furnace, you most likely won’t need to think about an air handler.
Air handlers are typically linked with heat pumps and manage airflow across your home. Some models also have extra heating and cooling components to assist the heat pump.
A furnace heats in a different manner by blowing warm air into your vents, which circulate it throughout your house. Because furnaces have combustion chambers to produce hot air, they don't need some of the components you'll find in a regular air handler.