Area rows on the Page Analysis table that begin with "Compare" contain statistics for the optional comparison page you selected on the second tab of the page critic window. If you don't select a compare page, then these lines will not appear.
This is useful in figuring out what makes one particular page "better" than yours. Keep in mind a page can do better than yours even though it may have fewer keywords or lower scores. More or higher is not always better!
Be wary of comparing to pages that just don't "make sense". Sometimes you'll run across pages that rank well for a variety of reasons even though the content does not appear to justify the ranking. That's why averages of top ranking pages can sometimes be more useful.