Terms TWEET – A message sent in Twitter – containing 140 characters or less.
Terms FOLLOW – In Twitter, you “follow” others and that allows you to read all of their tweets. If they desire, however, they can “block” you.
Terms @REPLY – A tweet which is sent in reply to someone else’s tweet. While a normal tweet is aimed at all of the people who follow you (and even those who don’t) a reply tweet is aimed at the person who originated the tweet.
Terms DM – DM stands for Direct Message. You can only send a direct message to someone if they are following you.