The evaporator coils on the front of the air conditioner get very cold during normal operation of the air conditioner. As the warm moist air in the room comes in contact with the cold evaporator the moisture in the air condenses out of the air and attaches to the evaporator coil. As more and more moisture condenses the water begins to drip down into the base of the air conditioner where it is evaporated to the outside of the house.