Air handlers and furnaces aren't usually used side by side in Kitchener. If you rely on a furnace, you probably don't need to think about an air handler.
Air handlers are usually paired with heat pumps and manage airflow around your house. Some systems also offer extra heating and cooling components to support the heat pump.
A furnace runs in a different manner by pushing heated air into your vents, which circulate it across your house. Because furnaces have combustion chambers to produce heat, they don't need some of the pieces you'll find in a regular air handler.