Google Tuesdays: Google Page Rank Explained by… Google
If the whole thing about Google Page Rank confuses you, the simplest way to explain it in laymans terms is that some links to your site count more than others, and that this is because Google considers some sites more “important” than others. Quantity counts, but Quality matters too.
You can read more about Google Page Rank from Google’s official explanation at their site.
Popularity: unranked

