Something about hashtags in Twitter
Answer: these are called hashtags in Twitter. Since Twitter does not provide any means to categorize or group the tweets, the twittercommunity started making use of hashtags to group tweets.
So how can you find all those tweets then?
Easy, take a look at http://search.twitter.com, and search for the hashtag of your choice. Thanks to the enormous popularity of Twitter, there are also numerous apps out there on the internet that help you with the use of hashtags, such as http://hashtags.org
You can follow me on twitter via http://twitter.com/icantinternet
And this time, if you see Hashtags in Twitter in your timeline you know what they are 😉