What is Impressions?
Impressions count displays, not people: every time the post appears on a screen is one impression, even for someone who has already seen it. That is why the number is always greater than or equal to reach, and the difference between the two says how many times, on average, each person saw the content. A high ratio on a carousel is a sign the network showed the post again, on the next slide, to people who did not swipe. In 2024 Instagram started merging impressions and plays into "views".