Air conditioning is all about heat and heat transfer. That is why every A/C system includes two heat exchangers. A heat excahanger is nothing more than a device that is designed to transfer heat from one substance to another.

In your A/C system, the heat exchangers are referred to as the evaporator and the condenser. In the case of the evaporator, it absorbs heat from the hot air passing over it. The heat is transferred from the air to the refrigerant in the evaporator. That heat transfer causes the refrigerant (freon) in the evaporator to boil and change state to vapor, but it doing that, it also removes the heat from the air so that the air entering the vehicle is cooler and more comfortable.

The A/C condenser is also a heat exchanger. Because the refrigerant absorbed heat in the evaporator, the vapor refrigerant is moved to the condenser in order to remove that heat. When the condenser removes the heat, it is transferred to the ambient air. In dong that, the vapor refrigerant is converted back to a liquid refrigerant, ready to enter the bottom of the evaporator to absorb more heat.

In the case of automotive air conditioning, the A/C condenser should always be kept clean and free of bugs and debris. When the condenser air flow becomes obstructed, the condenser is unable to provide the cooling or heat transfer required by the A/C system and cooling performance is reduced if not lost all together.