Air handlers and furnaces aren't typically found together in Rochester. If you have a furnace, you likely shouldn’t need to consider an air handler.
Air handlers are typically used with heat pumps and deliver airflow around your home. Some systems also provide secondary heating and cooling parts to assist the heat pump.
A furnace works in a different way by blowing warm air into your vents, which circulate it throughout your residence. As furnaces use combustion chambers to make heated air, they don't use some of the pieces you'll spot in a normal air handler.