Application Virtualization: How application streaming can be done via internet?

I know about packing a software as a virtual application through application virtualization products. But I really dont understand, How can they offer the streaming servi开发者_如何学运维ces of a package from a centralized server to the clients.

They call it as application streaming. Can someone explain it how that can be done.

Basically it's just virtualization, with bits delivered on-demand in the most optimal way possible.