How does 'Who can post comments on my story' privacy works?

Hello. In backend > Privacy I can see "Who can post comments on my story" (post.comment rule).
Can you please say more about it? How does it works?
It apply only for "Story posts" (stream item with text only)?
Or it apply to all types of stream items?

Or it also can disallow to comment videos, albums, photos?

thanks.