A Liebherr fridge with one cooling system cools the fridge and freezer compartments of your fridge at the same time. Most fridge freezer combinations work this way. The fridge has one thermostat that controls the temperature of both the fridge and the freezer. You can operate the fridge as a whole. A Liebherr fridge with DuoCooling cools the fridge and freezer compartments separately with 2 separate cooling systems. You can operate them separately.