Twitter Definitions (I found some of these definitions here, and have tweaked them slightly):

• Following:  The term for “friending” on Twitter.  When you follow someone, their tweets will show up in the feed on your Twitter homepage.  When someone follows you, your tweets will show up in the feed on their Twitter homepage.  Following does not have to be reciprocal, someone can follow you without you following them back, and vice versa.  Your Twitter homepage will give you a count of the number of people you are following and the number that are following you.
• Regular tweets: This is when you speak to all your followers by typing news, links or other information into your status update bar.  These tweets can also be seen by people who aren’t your followers and even by people who don’t have a Twitter account.
• Retweets (RTs): This is when you repost something someone else has said so that your followers see it.  Do this by typing RT, then space, then @username, then copying their tweet in its entirety. This is considered a huge compliment in Twitter World. You can also add your own take if there is space.  In TweetFunnel, you can just hit the RT button.
• Direct Messages (DMs) : This is for when you want to speak to only one person, and only he/she can read this tweet.  You can DM on twitter.com by using the “Direct Message” button. It will give you a drop-down menu for names, then you can just type your tweet in the status.  You can only DM people if you are following them AND they are following you.  In TweetFunnel, You can also DM by typing “D” then space, then the person’s username followed by your message—this works both in Twitter and in TweetFunnel.
• “At Replies” (@reply): This is the friendliest form of tweeting. You are responding directly to one person, but every one of your followers (and anyone else) can read it and can jump into the conversation. Do this by typing @username, then space, then your tweet. You can also do @replies on twitter.com by scrolling over the right side of a tweet message and hitting the “flip-around-looking arrow” that appears.  In TweetFunnel, just hit Reply next to the tweet.
• #/hashtag: Hashtags are a bit more complicated.  A hashtag is the # symbol followed by a word (ex: #travel). These are used when you want to participate in or follow a discussion on a specific subject or event.  It’s a bit like making a separate “room” for a discussion.  You can access this “room” by searching for the hashtag using Twitter Search.  Remember that this isn’t a private chat “room.”  For more on hashtags, click here.