To measure the quantity and/or quality of sites that link back to your Web site.
Link popularity is a ranking method used by most major search engines. It looks at the number of Web sites linking to your page and more importantly, the quality of who is linking to you. The more sites linking to you, the better your ranking becomes. Also, links from more popular and content relevant sites are better than just any random links (such as link farms).
To find out who is linking to your domain name, go to Google and enter the following in the search box (replacing "yoursite" with your domain name): link:www.yoursite.com Note: ONLY inbound links from websites with a pagerank" value of 4 or more will be listed.
Webmasters: Be sure to read the "more info" article in the page rank definition to understand Page Rank vs. Link Popularity and Linking Tips for BLOGS!
NetLingo Classification: Online Jargon