Air handlers and furnaces aren't typically used together in Voorhees. If you rely on a furnace, you probably shouldn’t need to think about an air handler.
Air handlers are typically linked with heat pumps and manage airflow around your residence. Some models also offer backup heating and cooling components to support the heat pump.
A furnace runs in a different way by blowing warm air into your vents, which circulate it throughout your house. As furnaces depend on combustion chambers to create heat, they don't use some of the components you'll find in a regular air handler.