The video prototype shows which user role (persona) wants to reach which goal with which benefit. Or also which problem is solved with which service or product. A step in between a user story and a video prototype can be a storyboard.At the “rapid paper based video prototyping” the usage of a paper prototype with changing states is filmed in a way that the interaction and reaction manner of the system becomes clear. Basis for that is a screen flow.
A list of tasks that should be accomplished in video prototyping has been mentioned on the MediaLabAmsterdam website.
Here is an example of video prototype for a mobile app.