Twitter Hashtags are a way of following tweets from different Twitter users, in one simple thread. Very simply, Hashtags allow you to watch a conversation, event, meme or topic evolve in real-time.
An example of a tweet with a Hashtag looks like this:
You can then proceed to follow all the tweets with that Hashtag – there are several ways to do this.
Here you will be notified when there are new tweets with that Hashtag, and you have to hit refresh in your browser, or hit F5.
Another way to do it, is to set up a specific feed in a Twitter application such as Tweetdeck which can be set to refresh in real time.
What is really interesting though, once you’ve got the hang of Hashtags, is to watch how small communities grow up around them, and then disappear again. A good example of this is the development of memes, which see people tweet about a particular cause, such as #ilovethenhs. And, at the moment, Twitter doesn’t track these and store them, so once they’re gone, they’re gone for good.