Heat pumps are a piece of equipment that forms part of a heating and cooling system. They are an alternative that is considered more environmentally friendly than a typical gas fired piece of equipment. In this system, an electrical pump exchanges heat from the cool side of a system to the warm side or vica versa.
As an example, in order to heat a space, cold air may be pumped into the unit, warmed up through internal ductwork and coils and than pumped to the exterior. Conversely the air can be pumped from the warm side, cooled via internal cold water and than ducted to the interior of the space.
Heat pumps operate via air, geothermal energy, solar or water.