A refrigerator is a cooling appliance for the storage and preservation of food. The freezer portion is designed to store frozen food; freezer is design to keep food and dairy products to avoid it from spoiling.
The working principle of a deep freezer is that the coils absorb heat from the surrounding air, but they can't do this if they're covered with ice or frost. This is why periodic defrosting is so important and why many freezers have an automatic defrost function
The freezer compresses the coolant, which heats it, and then passes the hot vapor around the coil at the back. Heat radiates from the coils to the kitchen and the coolant temperature drops