Glossary
What are impressions? And how they differ from reach
How many times your post got shown, counting the same person twice if they saw it twice.
An impression is one showing. Your post appeared on somebody's screen, and it got counted. If the same person scrolls past it three times, that is three impressions and one person.
Why the number looks so big
Because it double counts on purpose. Impressions are always the flattering number, which is exactly why platforms like putting it at the top of your dashboard.
What it is actually good for
Comparing one of your posts against another of your posts. Same account, same audience, so the double counting cancels out and the bigger number really did travel further.
What to pair it with
Always read it next to reach and engagement rate. Impressions tell you a post got shown, and those two tell you whether it landed on new people and whether anybody cared.