What a refrigerator really does is move heat. Do this together with your family. Rub an alcohol-soaked tissue onto the back of your hand. Watch the wet spots as you blow, and feel the temperature of your hand. You got really cold, and evaporation is the reason why.
Evaporation is when a liquid turns into a gas.
The heat it needed moved from your hand. Inside your refrigerator is a loop of pipes filled with a chemical that can do the same thing - change from a liquid to a gas and move heat as it evaporates. 1 - The liquid chemical is inside these pipes. Heat moves from your food to the liquid, which evaporates and turns into a gas. 2 - The gas goes into a compressor, which squeezes it back down in size until it becomes a liquid again.