Twitter users, what does this mean?

[Fearlessjudge324]

On twitter I often see a # before a Tweet. I know that @ is a reply, but what is #?

[om]

The # together with the phrase that follows the # is called a "hash tag" or "hashtag". The hashtag is a kind of label that indicates that this tweet belongs to some particular category or topic of discussion.

Twitter itself doesn't recognise hashtags and doesn't do anything special with them, but there are a bunch of other sites that monitor Twitter feeds and respond to hashtags in some way. Some sites rank hashtags by popularity, some let you view tweets grouped by hashtag and so on.

There is no organised or defined set of hashtags, you're free to make up your own. Obviously if you're really trying to use them to label tweets that deal with a particular topic then you want to find the hashtag value that other people are already using for that topic and use that same hashtag in your tweet.

Now that you know what they're called, if you want to know more then Google will find you a bazillion pages that talk about them. A couple to start with are http://www.techforluddites.com/2009/02/t...se-it.html