A compressor is a part of the fridge that converts the refrigerant from gas to liquid. It operates according to the temperature in the fridge and runs at full speed when it needs cooling down. Further, it stops completely when the temperature is low enough. An inverter compressor is a gas compressor that is operated with an inverter.  It works like a thermostat. It starts slowly, then increases its speed and as the desired temperature is reached, decreases it again just enough to maintain the temperature. In simple words, the temperature is regulated accurately as the desired requirement.