Find below the list of metrics with their respective definitions:
Users: Total number of unique users who tweeted using the hashtag in a tweet.
Messages: Total number of messages including tweets, retweets and replies.
Tweets: Total number of original tweets posted.
Retweets: Total number of retweets posted.
Replies: Total number of times users replied to a tweet.
Estimated Reach: Total number of followers who saw the hashtag.
Estimated Impressions: Total number of times the hashtag was seen by users.
Engagement: Total number of actions taken on the hashtag including retweets and likes.