Apart from the odd few, most people are not that interested in how refrigeration systems work, other than to try to understand what is causing a specific problem with their own appliance.
In very basic terms, your domestic refrigeration appliance is controlled by a simple heat exchanger along the lines of a heat pump. However, with modern fridge freezers, technology is now much more advanced and, especially the double door American style fridge freezers, are far more complex.
Importance of Refrigeration
In order to keep your stored food in as fresh a condition as possible within the refrigerator requires a steady temperature of:
2-5oC for cheese, fruit, salad etc.
-1-2oC for meat, fish etc