Twitter users - what does this mean?

[Miss Ohhh]

sometimes i see tweets with this : #______

what does the number symbol mean or what?
like, i have no clue whatsoever.


the first tweet on this twitter is an example:
http://twitter.com/mmitchelldaviss




thanksss.

[fjpoblam]

A # as the first letter of something marks what is called a "hash tag" and makes something easier for everyone to find. People use it, usually, to mark things other people talk about in common. For example, #followfriday is a "hashtag" people use (for what reason I haven't determined) to mark a list of Twitter userids that are interesting or worth "following". You'll have to look around and find other "hash tags" to find out which ones are being used, or you can "gamble" and make one up yourself, just by putting # in front of a word, if you think it'll be used by others for an interesting shared topic. See: http://hashtags.org/

P.S. all this searching may be done at search.twitter.com