Making a movable 3d scene from limited initial information. Some pros and cons against a traditional '3d model' approach. Pros - faster/simpler to generate (especially with lots of data), better at dealing with light and reflection. Cons - Having 3d geomtry can be useful eg. for collision detection, volumetric understanding, surface alteration/deformation etc.

Not much widespread use right now - Possible commercial use cases are things like real estate walkthroughs and maybe replacing a google street view with something more interactive.