What is a Hashtag (#) or Pound Sign on Twitter?

A "hashtag" , or a pound sign, is a Twitter term for the symbol that looks like this: #

When used in Twitter, the hashtag signals that the person Twittering is referring to a subject, or common theme or topic that other people are talking about in Twitter.

Here's a good article that defines the hashtag and gives a bit of history. Side note: funny that 'history' now defines something that is not even a year old, as of this post.

TECHNICAL USES OF THE HASHTAG #
A technical side effect of using this term, is that depending on how you are accessing Twitter, either from TweetDeck, Tweetie, or the regular old fashioned way at www.Twitter.com, Twitter will activate the phrase that directly follows the #. Here is an example of the # (hashtag) in use:

@ktjames I love to follow @collectivee, @sabinaredbranch, @bethschoenfeldt, @popjudaica @TheEllenShow, #followfriday

This is an example from a tweet from me, @ktjames, to my followers. I am telling them that I like to follow these Twitterers (remember, the Twitter name is offset by the @ symbol, and Twitter automatically makes it a link for you). I end it with #followfriday. This hashtag phrase is a commonly used phrase that people us on Fridays to tell their followers who else they like to follow. It helps spread the Twitter love by helping your Twitter friends gain followers.

BRANDING AND YOUR HASHTAGS #
Anyone can make up their own reason for a #, but it's up to the Twitter community to pick it up and use the hashtag. If you are going to make up your own hashtag, keep in mind that what makes sense to you, might not make sense to your followers, or potential new followers. #followfriday is a nice example because it states what it is: It is an activity that happens on a Friday when people shout out who they like to follow.

If I were to make up a hashtag for an event series at Collective-E for our Industry Insights, I could name it: "#CEII", which could stand for "Collective-E Industry Insights". But that probably would not make much sense to you. A more effective hash tag could be: "#industryinsights". Yes it takes more space, but it gets to the point.

If I were to make up a hashtag for the brand of this blog, I could call it "#kjpblog", which would stand for Katie James Pixelated Blog. You tell me if that would catch on or not. ;) I use KJP to refer to my brand, but I would need to become pretty solid in my brand for others to recognize the acronym. I would also need to tweet a lot about my blog. Maybe I'll try it and report back. ;)

Have you created any hashtags? And have they taken off?