The page history as represented by the journal, at the bottom of the page, provides a linear view into history. What you see will depend on where you are standing.
The journal, at the bottom of the page, gives a partial view of the page's history. Partial because it is just the history that has created the view of the page you are seeing. But, as the page gets forked other possible versions of the page get created. The other possible versions that are in your neighbourhood are listed above the page title as new, older or the same.
It is also important that just because there are possible versions listed at the top of the page. They may not share any history with this page, just share page title.
Newer, Older and Same just tells us when the last edit event was, in relation to the last edit on the version of the page being viewed. With time recorded down to the millisecond, pages that are the same are in all probability a fork of one another.
Hovering over an action in the journal highlights the item on the page that it is for, but only if the item has not been deleted. Its place in the journal, in relation to any fork events informs us the site the action originated on - and indirectly who made the change (assuming that site has been claimed). To discover the changes an edit action made we would have to compare a before and after view - by using Shift + click on the journal, to view different versions of the page side by side.