Facebook Basics: Analytics Changes
As the administrator of a Facebook page you are given access to see insights into your posts, followers and other juicy information. In the past each post you made was given an "Impression" score, which was the amount of times your post was seen by Facebook users.
Recently Facebook changed this metric from "Impressions" to something a bit more solid, "People Reached".
People reached displays the exact number of people that saw your post, a changes which adds a little bit more meaning.
Switching to people reached is a positive move for Facebook's newly improved insights package. Better statistics can help businesses using Facebook understand how their engagement is perceived by followers and help change their content strategy accordingly. If you have 1000 followers and you post a video which only reaches 100 of them, perhaps you're not posting at the right time of day.