It's like this. You find a page that is orphaned. You decide some of the content is useful in !WikiPageA and some is useful in !WikiPageB. So, you copy and paste some to A and some to B, and then clear the original page (and tag it with ?DeleteMe) ... you have refactored some content into a new place.
Maybe you find that there is a page that's been dragging on with lots of comments, and you'd like to summarize them. You re-work all the comments into a new page (or the same page) that just contains the information, not the discussion, and move all the discussion to OriginalPageDiscussion or something, or stick them at the bottom. Refactoring.