The statistic will be one of four tracked by Pages Insights. The purpose is to let page admins better understand how their ranking stands for the page in terms of comments and interaction.
While People Talking About may not be the final name for the metric, the tool will measure all user interaction related to interacting such as answering questions, posting to the wall, etc.
How many Likes your posts acquire has become a standard objective for Facebook campaigns, but the metric has come under criticism for being too limited a tool for gauging the success of advertising efforts on the site.
Pages Insights will also provide more background about certain updates. For example, Facebook some time ago began tracking user’s posts, and now it will list the last 500 user posts, and use the data to report the total number of engaged users, People Talking About, and the percent of users who posted a comment.
Here's what some of the top influential social personalities and everyday users had to say about the announcement: