Tweet
Each of your Twitter posts or updates is known as a tweet. Some people refer to them as "twits," but the official term is "tweet."

@
The @ symbol is a way of referring to another Twitter user. For example, @SandeSaimond means you're either sending a message to Sande Saimond or you're talking about her in your message. On your Twitter home page, you'll see a linked search where you can find people mentioning your username with an @ before it. This is how you find other people's replies to you.

Retweet
A retweet - or RT - is when you share the tweet of one user with all of your Twitter followers. If you happen to follow a Twitter news feed and they post a link to a story that you feel should be shared, you can "retweet" it. If you see a beautiful quote or a funny saying that you like, you can also retweet it. For instance, if I (SandeSaimond) tweeted, "Twitter Tips - How To Tweet in 140 Characters or Less http://ow.ly/5ntl" you could retweet that as: "RT @SandeSaimond: Twitter Tips - How To Tweet in 140 Characters or Less http://ow.ly/5ntl." Something to be aware of - it's considered rude or just plain not nice to take someone else's Tweet and send it back out as your own. Give credit for the tweet where it's due. You will more than likely be thanked for the Retweet and you may gain new followers at the same time. Retweets are usually prefaced with "RT @username."

Reply
Reply is when you respond to a tweet from a particular user. To reply to any given Twitter community member where it's placed in the public feed (everyone can see what you are saying) is called a Reply. Most Twitter clients (and Twitter itself) prefaces your tweet with "@username." If you wanted to send a message to me, for example, you would tweet, "@SandeSaimond How are you today, Sande? Hear any good tweets?"

Direct Message
Whereas replies are completely public, a direct message is akin to a private message that you send through a discussion board. You can only send a direct message to someone that is following your account. Send a direct message by prefacing your tweet with "DM username."

Follower
While Facebook requires that all relationships be reciprocal, Twitter allows for one-way relationships. If you find Twitter users who are interesting, you can "follow them" to subscribe to their tweets. They do not necessarily have to follow you back, though the more social users will want to follow you back.

Tweeple or Twerson
Twitter people, Twitter members, Twitter users.

Tweeps
Twitter people that follow each other from one social media/network to another.

Twitterverse
The Twitter Universe ... it's big and it's expanding at a great rate!

Hash Tags or #
Hash tags are words or acronyms that begin with the number sign. They are used when many people are tweeting about the same topic or from the same event. At least one hash tag is often atop Twitter's trending topics list. The granddaddy of tracking what the different hashtags means is http://www.Hashtags.org, which tracks tags by popularity over time. Before Twitter's search feature was useful, Hashtags provided a means to search tags. A popular hashtag is #FollowFriday. You'll see every Friday posts from different tweople suggesting who they think you should follow. "#FollowFriday @SandeSaimond."