A heat pump is very simply a device or appliance that moves heat from one place to another usually via a refrigerant cycle. As part of the refrigerant cycle, you do boil the refrigerant in order to extract the heat after the compressor cycle. So a very small part of the cycle can be considered a boiler of sorts.
Whilst there are several types of heat pump ie ASHP, GSHP, STHP, etc we will mostly address ASHP and GSHP. There are sometimes other variations although these are rare generally and suited to a very small set of use cases.
Air Source Heat Pump (ASHP)
– There are 2 main types of ASHP. A2A and A2W. An air conditioning unit which can be found in many places is classed as an A2A. You have an outside unit that is mainly the compressor and fan, also an inside unit which moves the air around and to which the refrigerant flows to and from.
Ground Source Heat Pump (GSHP)
– There are a few sub types, however the most common is closed ground loop systems via a 2d surface layout (horizontal), 2d trench layout (vertical/horizontal) and a bore system layout (straight down borehole).
Even within these types of systems, you can get combinations of systems to produce a hybrid system. Commonly lets say a boiler paired with an ashp (a2w)