What does # and @ mean on Twitter?

[Empire539]

@ is used to directly reply to someone, or at least mention them. So if you wanted to send me a reply because I made an interesting tweet, you might put "@empire539 you are so awesome!" You can also simply mention someone's name, if you want them to be aware of it, such as "I think @empire539 is a great answerer!"

# are called hash tags. They're usually used to denote something that's trending. Say if it's the series premier of a show, then you might put "omg i cant wait for #jerseyshore tonite". But hash tags can pretty much be about anything.

You may also find the following links helpful:
http://support.twitter.com/articles/1402...d-mentions
http://support.twitter.com/articles/4930...gs-symbols