Refrigerant gas fluids absorb the heat of low temperature items(ambient air) in the evaporator.
The refrigerant gas comes out from the evaporator, and turns into high temp & high pressure gas via the compressor.
High temp & high pressure gas releases the heat to the items(water) in the condenser, and turns to be high pressure liquid
High pressure liquid decompresses the pressure in the throttling device, and turns to be over-heat liquid media, and goes into evaporator, the primal procedure of circulation.
Heating pump is the device to enhance (or transfer) the heat, the function is to absorb the heat from the environment, and transfer the heat to the high temperature object, the working principle is to work as per reverse Cannot cycle, the same as refrigerator.
When the heating pump is working, it will consume a part of energy itself, and transfers the energy of ambient medium, via the heat transfer fluids circulation system to raise the temperature and use. The spent power of whole heating pump device is just the small part of the output power, so the heating pump technique will save plenty of energy.