This allows a world author to save a snapshot of the world to local disk, and later on restoring the world as it was in the snapshot. There are multiple usage scenarios, but one that immediately springs to my mind is the improved ability to perform iterative world editing. By being able to reset the world back to a known working state it's much easier to try out new configurations and behaviour.
All work is currently being done on separate branches of both Ember and Cyphesis. The following video shows the status of this feature some weeks ago; it has progressed even more since.