Air handlers and furnaces aren't typically installed side by side in Kitchener. If you use a furnace, you probably don't need to think about an air handler.
Air handlers are usually paired with heat pumps and manage airflow across your house. Some units also have extra heating and cooling components to assist the heat pump.
A furnace heats in a different way by sending warm air into your vents, which circulate it around your house. As furnaces depend on combustion chambers to create heat, they don't need some of the pieces you'll find in a standard air handler.