Facebook considers a “story” every quote, comment, check-in, like, rating, or post that appears in users’ news feeds. This metric represents the total number of stories created by the users. It is common for a user to create 2 stories per period.
“Story” is a very relevant engagement metric as it represents a brand display in users’ News Feed. Do you know when you are on Facebook and it appears that a friend commented or liked a Page X post? This is a Story your friend created for Page X.
In the report you can see the description of the metrics by clicking on the “?” Icon.