These are the heat-exchanging tubes at the back of your refrigerator. The gas cools and condenses into liquid as the heat leaves. The cycle repeats with the cool liquid refrigerant shooting through the expansion valve etc. The expansion valve allows the cool liquid to expand and evaporate as a gas. The evaporation results in a dramatic drop in temperature.
Pressure is proportional to temperature.
Evaporation of a liquid takes away heat. Heat exchanging tubes inside the refrigerator. Heat moves from warmer areas to colder areas. As heat leaves, the food compartment gets colder. Meanwhile, the gaseous refrigerant is being warmed.