you don’t have to be on twitter long to see that there are lots of people using hashtags, #[followed by a word or acronym], and you may be wondering what they are used for and why you would want to use them. here is a brief explanation:

“Twitter messages may be tagged using hashtags, a word or phrase prefixed with a #, such as #beer.[31] This enables tweets on a specific subject to be found by simply searching for their common hashtag, provided that the user has tagged his or her tweet.” (via wikipedia)you can then search twitter search for all the tweets with those hashtags.additional blog posts and articles on hashtags:
making sense of confusing twitter hashtags