What does Summarize Photos setting do?

[WinterWolf90]

I am not sure if this is new in iOS9 or if I have never noticed it before, but what does it do? I tried turning it off and on and checking it to see what it does, but I couldn't pin point it.

 

[Gav2k]

It increases the details in the collections screen. Sorry to be specific it reduces the number of photos shown. If for example you take multiple shots over a time period it's show 1-2 of those till you expand the view.