A heat pump moves heat from one location to another mechanically. The most common types of heat pumps are air-source heat pumps and ground-source heat pumps. What these do is keep your home warm in winter and cool in summer. Air-source heat pumps pull heat inside from the outdoor air in winter and from indoor air in summer. Using a heat pump, heat is extracted when you want to keep your home cool, or drawn in when you want to keep it warm.