Explain Windows Search ranking to me.

Let’s say I’ve decided to bear down and write the novel about Athena’s ascension to the throne of Olympus, an idea I’ve been toying with for years. I’ve got tons of material about Greek mythology–text and images both–on my hard drive, from various other projects, and decide I want to gather all the Athena stuff in one folder. So I open the Libraries window (I’m running Windows 8) and type *Athena *in the search field and press enter. The search result are grouped by Search Ranking, in descending order. The highest ranked results are NOT any of the articles or pictures with “Athena” in the title, nor those articles in which that name appears multiple times, or those images with a face tagged as “Athena.” No, the highest ranked item is an article I wrote about the Nemean Lion 10 years back, in which the word Athena appears exactly once. Thinking perhaps that “ascending” and “descending” mean something different than I am expecting, I change the sorting accordingly, and now the highest ranked item is an article comparing Greek and Latin grammar, in which the word Athena, again, appears exactly once. Documents actually titled “Athena,” in which the word appears dozens of times, are never the top search result; likewise pictures of sculptures of Athena, titled as such.

Why is this? What does the search ranking in Windows 8 actually denote?

Incidentally, I am NOT asking how to most efficiently use Windows 8 search. If I’d been actually looking for the Documents about Athena, I’d have started my search in the documents folder and typed name:Athena in the search field; likewise, if I’d been looking for pictures, I’d have done a name, tag, or person search in the Pictures folder. I’m just wondering what the Search Ranking is supposed to be about.