• Google acquired Postrank last year, and 5 upgraded reports illustrate your content's social media impact.
• The reports provide a "score" to content based on social metrics, with each providing different insight.
• Reports include Overview Report, Conversions Report, Social Sources, Social Plugins, and Activity Stream.  Google's overview of each report can be found here.
   

From the article:

Following Google’s acquisition of PostRank, social reporting has been upgraded inside Google Analytics to incorporate five new reports. These reports “score” content based on the number of comments received, links, mentions, tweets, and other social media metrics. Each report provides a different insight for a variety of your social reporting/monitoring needs.

1. Overview Report, which highlights the impact of social media on content. This report breaks content down by “Last Interaction” and “Assisted Social Conversations.” For instance, you can find out the last time a user checked out your content through the social media platform, and the last time users actually both accessed and converted through...