Twitter Speak – Some basic definitions to get you started!

Tweet	A post on Twitter. 140 characters maximum! Note: There is no way to edit a tweet. You can delete, but it will still be cached on Twitter in search.
Follow	To subscribe to someone’s Twitter stream (you get updates on your homepage).
Unfollow	To unsubscribe from someone’s Twitter stream
Block	Set it so someone cannot follow you or see your tweets when they’re logged in. Too many “blocks” and that person will get banned from Twitter.
@User (mention)	When you mention someone in your tweet who has Twitter, be sure to use the @ sign in front of their name. When someone does this to you, it will show up in a different place in Twitter so you’ll be sure to see it. This is the best way to get the attention of someone on Twitter. Note: Twitter is smart and will figure out that punctuation after the name is not part of the username.
Direct Message (DM)	This is a private message that will only go to the person you send it to. To send, type “DM @Username Then your message.” Be careful, if you fat finger this one, it will display publicly to the whole world
The hash tag #	To add a tag to your tweet, use the pound sign and then the tag (i.e. #earthday). This way, people can search for the hash tag and find all things related to a conference, event, or other topic.
Tiny URLs – Or bit.ly!	The 140 character limit means URLs should be as short as possible. There are free services that allow you to create a short URL that will redirect to the full long one when visited. I use bit.ly (http://bit.ly) because it gives you reports on how many people are visiting your links.
The retweet – RT	If you like what someone says in a tweet, you can quote them by “retweeting.” Essentially, copy and paste what they say and add “RT @Username:” before it.
The hat tip – HT	It’s ok to shorten a little if you’re retweeting and hitting 140 characters, but if you’re going to completely paraphrase (or completely restate), use a hat tip (HT).
Overheard – OH	Use this to quote anonymously. I.e. OH: “Funny quote I just heard.”