As you create a storyboard, its panels and their drawing layers are all containing inside the storyboard track. However, it is also possible to add video tracks to your animatic, in which you can add image and video clips that will appear over or underneath the artwork in your storyboard.
Video tracks can serve as multitude of purposes: For example, they allow you to use images and videos as references for your artwork or animation, add overlaying logos to the storyboard, import premade opening and credit sequences, make backgrounds span over several panels or scenes and insert live action sequences.
The images and videos you add to video tracks are independent from your animatic. They are not bound to a panel or to a scene, and they are not affected by camera movements.