Impressions are the number of times a message has been seen.
Impressions are how many times your message has actually been seen, letting you know that someone has taken notice versus ignored the message they received.
Sometimes "impressions" are referred to as views or opens; impressions are a great indicator that someone is taking notice.
You can find analytics like impressions under [Engagement Reports]. Click here to learn how to get there.
Or you can find the number of impressions under any piece of content. Go to [Review] on any post, then click [Reports].