What Is the difference between VAV system and VRV system in air-conditioning?

there is a huge difference between both.

VAV : Variable Air Volume

automated damper box controls the quantity of air passing to a specific area , exists in AHU's System

VRV : Variable refrigerant volume 

Central Condenser units that controls more than one indoor unit , its a closed DX system 

VAV stands for veritable air volume which controlls the flow of air volume  and VRV is stands for variable refrigerant volume which controlls the flow of refrigerant in refrigerant piping system in direct expansion system

I believe the answer by Mr Muhammad is enough .