Could you tell me What are that "AirflowNetwork" and "Airloop" in Energyplus?

Hi everyone I can't understand two classes "AirflowNetwork" and "Airloop" Could you tell me that? Additionaly, could you tell me what are different of two classes "AirflowNetwork" and "Airloop"

The Airloop is the HVAC system, which usually serve multiple zones, has a fan and cooling/heating coils, and operates either using a Thermostat/humidistat or air temperature/moisture set point control. See AirloopHVAC object.

The AirflowNetwork is a pressure/airflow model that is used to simulate building air flow in more detail. You would usually not use AirflowNetwork to initially create and simulate the building. When everything is set up and working AirflowNetwork could be used to simulate the building in more detail, if needed.