Popularity of Your Site
The methods that search engines use to rate popularity are, of course, highly confidential (search engining is a cutthroat business), but popularity has something to do with how many sites link to you and how many people click through on their search results to your page. If you're popular, you are ranked higher than a less-popular site.
Popularity Equals Amount of Content. The More Content You've, The More Traffic = The More Popularity.
Why we know mashable.com, because it has over 20 million visitors. and over 14 million pages. (in blogs its articles and in sites its pages). Now you can easily know how much popular = content = traffic you have.