Refrigerators keep food cold. A refrigerator is a big box with a door you can open. You keep some foods in a refrigerator so they won't spoil as quickly. The walls of the refrigerator are filled with insulation. This keeps the cold air inside and the warm air outside the refrigerator. Refrigerators need electricity to work. They have small electric motors. The refrigerator must be plugged into an electrical socket. The electric motor operates the compressor.
A chemical called a refrigerant is used to keep it cold inside. The refrigerant flows through a closed loop of pipes or tubes hidden inside the walls of the refrigerator. This chemical can easily change states from a liquid to a gas. Part of the loop is exposed to the air inside the refrigerator. Part of the loop is exposed to the outside air.
The refrigerant starts out as a gas. It is then compressed (squeezed) by the compressor until it turns into a liquid. The compressor squeezes the gas into a very small space. The gas turns into a liquid from all the pressure.