An air conditioner is a device that transfers heat from a room to the outside in order to chill the room down.

Through ventilation, the cold air can then be distributed throughout a building.
Because the Second Law of Thermodynamics forbids entropy from naturally decreasing, it takes work to operate an air conditioner.

Similar to a heat pump, air conditioners operate on a cooling cycle.
In the evaporator, a cold liquid refrigerant absorbs heat from the hotter area, cooling the space.
The refrigerant is then compressed to raise its temperature as it transitions from liquid to gas.

The heat from the refrigerant is subsequently transferred to the outside air as it passes through the condenser coils.
In order to lower its pressure and drop down to below the room’s temperature and start the cycle all over again, refrigerant expands.
Due to the presence of both an inside unit and an exterior unit (the condenser), air conditioners are referred to as “split systems” (the evaporator).

Both cooling and dehumidifying an interior space are tasks that these two technologies together complete.