"People Talking About This is the number of unique users who have created a “story” about a page in a seven-day period. On Facebook, stories are items that display in News Feed. Users create stories when they:
like a page
post on the page wall
like a post
comment on a post
share a post
answer a question
RSVP to a page’s event
mention the page in a post
tag the page in a photo
check in at a place
share a check-in deal
like a check-in deal
write a recommendation"