An air source heat pump has:

A condenser is made up of a plate heat exchanger.
A rotary compressor.
An enclosed finned tube heat exchanger (evaporator).
A big fan to convect air over the evaporator.
A motorised valve.
A pump to circulate water through the plate heat exchanger.

A solar assisted heat pump has only:
A reciprocating compressor.
An externally sited aluminium roll bond heat exchanger (evaporator).
Solar assisted heat pumps gain efficiency boosts from solar irradiance on the externally located and exposed, big surface area, aluminium roll bond heat exchanger panel when the sun is shining down on it in addition to absorbing heat from the outside air.

In summary, solar assisted heat pumps operate on the same fundamental principles as air source heat pumps, but they use passive convection (wind) rather than forced convection, which eliminates the need for fans. Additionally, they heat water directly, eliminating the need for pumps, plate heat exchangers, or motorised valves, which results in fewer moving parts, less frequent maintenance, lower electrical consumption, and low noise levels. Finally, they make use of solar irradiance.