Air conditioners and heat pumps will often look identical in design, foot print, etc. As with normal split system air conditioning above, a heat pump can be used instead of an air conditioning unit to keep homes comfortable all year long.
During the summer months, a heat pump draws heat out of your home to cool it. In the winter, it draws heat from outside air into your home to warm it (even though air may be cold in the winter, there is heat in the air and a heat pump system balances between this and using the furnace).
Additionally, a properly matched heat pump and furnace offer high energy efficiency for winter months as such a system can intelligently switch between heating sources for the least power/gas consumption. Heat pump efficiency is measured in SEER (cooling) and HSPF (heating).