Why does the fridge get cold?
For grown-ups: the science
The fridge gets cold because it carries the heat from inside out to the outside.
A refrigerator is a heat pump: a substance called refrigerant evaporates, gets compressed, and condenses inside its tubing. Inside the fridge, the refrigerant evaporates in the evaporator coils and absorbs heat from the air; the compressor then raises its temperature, and the condenser outside the fridge releases that heat. That's why the back or sides of the fridge feel warm - they're venting that heat plus the extra heat made by the compressor's work.
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Transcript
Have you noticed how chilly it feels when you open the fridge? Why does it stay so cold in there?
Inside the fridge, a special gas swirls through thin tubes. That gas soaks up the heat from the air around your food.
The gas travels through the tubes to the back of the fridge. It lets go of that heat outside, which is why the inside turns cold.
When you open the door, warm air sneaks inside. That's why the fridge keeps carrying heat back outside again and again.
The fridge stays cold because it keeps carrying the heat from inside out to the outside.