Short answer: The Collection is like the Voiij back-up—all observations added to the Voiij will be saved in the Collection.
It is unstructured, meaning observations are added to the Collection in the order they are made or uploaded, and you cannot change the order. (You’ll have more control over this in the actual Story.)
Every observation is automatically housed in the Collection, even if it’s added directly to a Story. If an observation is removed from a Story, a copy will still remain in the Collection for safekeeping.