EdgeRank… It is used by the Facebook system to rank your wall posts and page posts to help determine if they will show up in your friends’/fans’ news feeds. Bascially it measure the exposure a post has within Facebook.
Here are some good resources to read up on EdgeRank and how it can impact your business:
Edge Rank: What does it means for Brands?
6 Tips to increase your Facebook EdgeRank & Exposure
The Next Web’s post on everything you need to know about EdgeRank