Example: document d1 cotains a field called points with the value 100, and document d2 cotains a field called points with the value 101, if the index ranks is set to somthing like -points, then the rank for d1 is 2, and the rank for d2 is 1, simply sorting the documents, this is usefull in meny instances like, because to this day there is no esey way to sort a collection by a field