What is the difference between 2-pipe and 3-pipe in Inverter VRF (Variable Refrigerant Flow) air conditioning systems?

In 2-pipe Inverter VRF air conditioning system we may choose only cooling or only heating for all the rooms, depending on the season. On the contrary, with 3-pipe Inverter VRF air conditioning system we may choose at the same time heating for some rooms of a building and cooling for some others, in accordance to their needs. So, in combination with the DC Inverter compressors and the electronic control of the installation, it is created the best comfort in all the rooms according to their needs and not the season. In addition, we exploit the heat that is recovered by the simultaneous operation of heating and cooling, resulting in the increase of the unit efficiency and therefore lower operating cost.