An Air Conditioner is basically a refrigerator without an insulated box. It uses the evaporation of a refrigerant like Puron (410A) to provide cooling. 

1. The compressor squeezes the refrigerant causing it to become a hot high-pressure gas.
2. The hot gas runs through a set of coils where it quickly gives off its heat and condenses into a liquid.
3. The liquid refrigerant runs through an expansion valve, and in the process it evaporates to become a cold, low-pressure gas.
4. This cold gas runs through a set of coils that allows the gas to absorb heat and cool down the air inside the building.