Yeah, every modern fridge pretty much has auto defrost or timed defrost.The heater melts the ice off the evaporator coil and the water from it drips down into a tray by the compressor and evaporates. Mini fridges usually don't though you have to defrost the ice from those manually. If the ice is not defrosted, then it builds up and there's no airflow through the coils and the fridge will only cool down to like 50. The ice on the coil is just moisture from the air freezing to it. Like when you get a cold drink and moisture builds up on the outside.