URL Clicks: A count of how many times a URL in the Tweet has been clicked
Engagement: Engagement quantifies how much user interaction there is with your campaign. Engagements include all clicks on your Tweet, including Retweets, replies, likes, poll votes, and hashtag clicks — and earned clicks you're not billed for
Follows: To follow someone on Twitter means to subscribe to their Tweets or updates on the site
Retweets: A Tweet by another user, forwarded to you by someone you follow. Often used to spread news or share valuable findings on Twitter. You can also Retweet any Tweet to add to your own stream and share with your followers.