The Facebook Insights view that shows a Page Administrator the number how many people have been exposed to a specific post.

Why is the Facebook Reach Tab Important?

The Reach Tab in the Facebook Insights dashboard allows marketers to see which types of content and marketing methods are most effective. For example, within the Reach Tab, you can see how many people were reached by viral, organic, or paid Facebook content. This allows marketers to adjust their strategy and make better marketing decisions.

The Facebook Reach people gives insight into how content reaches users.