Impressions are the number of times a post from your Page is displayed. People may see multiple impressions of the same post. For example, if someone sees a Page update in News Feed and then sees that same update when a friend shares it, that would count as 2 impressions.

Reach is the number of people who received impressions of a Page post. Reach might be less than impressions because one person can see multiple impressions. For example, if a person sees a Page update in News Feed and then sees that same update when a friend shares it, that would represent a reach count of one.