Basically a conventional thermostat is an electrical switch that turns a certain circuit on or off according to the temperature range of its sensor.
Your contacts (platinum) can be opened or closed. This opening or closing occurs through the expansion or contraction of a fluid, gas whose pressure variation is proportional to the ambient temperature, confined in a chamber, which can be composed of what we call the bulb and diaphragm.
In this sense, it acts as a thermometer, except that the thermostat is not a simple temperature measuring instrument but a more complex device.
In addition to being sensitive to temperature fluctuations, it is also capable of automatically switching the electrical circuit of the appliance on and off as the temperature changes at the point where the bulb end (sensor) is in contact with the evaporator. This ensures that the proper temperature is maintained in the refrigerator.
Thus, when the temperature of the refrigerated compartment rises above the set temperature, the thermostat turns on the cooling system, which remains on as long as the desired temperature is not reached.
