Twitter: what does "#" before trending topic means?

[Fleur]

[greatcub844]

means number I think.

[Beanboy]

the symbol means "number" but i have never been on twitter. does it look like "#200. who likes twitter"

[Natalia]

it means code..

follow me on twitter =))

http://www.twitter.com/thepinkpradaa

[James]

Everyone who has answered so far is wrong.

# is what makes a 'hashtag'. A popular hastag at the moment is #iranelection. When you put hash in front of a phrase it means your tweet will become more visible ny anyone who searches for #iranelection. using hashtags make it easier to see who is talking about what and find people who are interested in what you are. Hashtags such as #lol and #funny are good to search for as it is an easier way of finding funny links or tweets.

Thanks for reading, I hope that helps.