Cycle:
Compressor - Work done by the compressor goes into compressing a low-pressure gas like Freon into a high-pressure superheated gas. The mechanical work is converted into creating a high-temperature, high-pressure vapor.

Condenser - As the high-pressure superheated vapor goes through the condenser it loses heat, goes through a phase transition to become a liquid, still at high pressure. When used as a heat pump, the heat extracted can be used to heat a house. For a refrigerator, this heat is dumped to the environment. It is the warm air you feel on your feet when standing in front of the refrigerator in the middle of the night. The condenser is prominent on the backs of most refrigerators as a vertical grating of coils.

Expansion Throttling Valve - When the high-pressure liquid passes through the expansion valve it expands rapidly into a region of lower pressure and greatly reduces both its temperature and pressure - still remaining a liquid.

Evaporator - As the cold, low-pressure liquid goes through the evaporator it absorbs heat, and changes phase back to a low-pressure gas. When used as a refrigerator, the absorbed heat can be used to cool down in inside of a refrigerating compartment. When used as heat pump, this heat is drawn from some external heat reservoir such as the air or the ground, some of which is later dumped in the heated area.

Heat Pump	Refrigerator
Qcond is used to heat something like a house. Then Qhouse = Qcond is heat delivered to the house. Qevap comes from outside source such as the air. Then Qoutside = Qevap is the heat extracted from the outside. You pay for the energy to run the compressor Wcomp but not for Qoutside.	Qcond is the heat dumped outside the cooling area. For a house refrigerator, Qroom = Qcond is heat dumped into the room where the refrigerator is located. Qevap is heat taken from inside the area to be cooled - the inside of the refrigerator. Then Qevap = Qcooler is heat extracted. You pay for the energy to run the compressor Wcomp. The energy dumped into the room Wcomp + Qcond goes into heating the air.

Working Fluid: Often the working fluid is a substance like Freon that will change phase from liquid to vapor at the temperatures associated with environment and cooling compartment. By adjusting the pressure in the condenser one can make Freon condense at room temperature. In a similar manner one can adjust the pressure in the evaporator so that Freon boils at the low temperature of the cooling compartment.