Can anybody explain me how VAV works with simple sketch?
Thanks

Somehow this seems like homework.

There are three types of VAV boxes

1- Bypass type:
The simplest. Inside the BOX there is a damper which modully divert the air to supply air diffusers and to return air plenum. AHU should provide air at constant temperature constant volume

2- Shut off type
There is a damper inside that modulate the amount of air the supply diffuser (it doesnot divert to return air plenum) The air handling unit has to have VFD. Thus AHu should provide air at variable volume but sstill constant temperature.

3- System powered type:
Old system, rarely used these days. It depends on the air pressure to operated it.