A Twitter impression is defined as the number of times a Twitter message is seen. This can be through search results, other people’s timelines, or Retweets. An engagement, on the other hand, is an action that is taken on a Tweet. This includes Retweets, @replies, follows, clicks on links, media views, and more. Because they are measured differently, it’s possible to have a high number of impressions but low engagement or vice versa. Impressions measure your reach while engagements measure how effective your message is.