Virtual desktop interface is a form of desktop virtualization, whereas desktop virtualization is itself a different entity that is separated with others.

VDI create a virtual machine and execute the user's desktop inside it, whereas desktop virtualization allows running the customized desktop without any virtual machines.

VDI works only for few users that have different demands but it is unsuitable to meet all the demands for all users, whereas desktop virtualization meet and provide all the required features to the user.