Hi, resources like videos, images and other kind of resources are usually stored in the "assets" directory of your Android project; these resources are then packaged together in the APK when you build your app.
Some resources can also be stored in the res/ folder (e.g. you may put an audio file under /res/raw, to make some sound effects...just as example);
Of course, nothing prevents you from creating an app that retrieves some resources from a server over the web, or that loads an image from the SDCard of your phone.
Android SDK provides API to support all of the above;
so, with Vuforia SDK you can leverage the full API of the Android SDK to build very sophisticated apps if you like.
To get started, I recommend that you star reading the DevGuide of Vuforia and that you look at the various samples, which will introduce you gradually to the different features of Vuforia.
Also, note that in the download page (at https://ar.qualcomm.at/sdk ) you can also find a sample called VideoPlayback that shows how to play a video/movie when a target is detected by Vuforia; also, if your device supports Android Ice Cream Sandwich (v4.0) or above, you should be able to see the video played directly on the target itself in 3D space (i.e. as a Texture applied on the target)
I hope this helps!