ⓘ Instagram Reach
Total number of unique users who have viewed at least one of the IG User's IG Media. Repeat views and views across different IG Media owned by the IG User by the same user are only counted as a single view.
ⓘ Instagram Impression
Total number of times the IG User's IG Media have been viewed. Includes ad activity generated through the API, Facebook ads interfaces, and the Promote feature. Does not include profile views.
ⓘ Facebook Page Engaged Users
The number of people who engaged with your Page. Engagement includes any click.
ⓘ Facebook Page Impression
The number of times your Page's post entered a person's screen. Posts include statuses, photos, links, videos and more.