Definition The # symbol, called a hashtag, is used to mark keywords or topics in a Tweet. It was created organically by Twitter users as a way to categorize messages
Using hashtags to categorize Tweets by keyword:
People use the hashtag symbol # before a relevant keyword or phrase (no spaces) in their Tweet to categorize those Tweets and help them show more easily in Twitter Search.
Clicking on a hashtagged word in any message shows you all other Tweets marked with that keyword..
Hashtags can occur anywhere in the Tweet – at the beginning, middle, or end.
Hashtagged words that become very popular are often Trending Topics.
Example: In the Tweet below, @eddie included the hashtag #FF. Users created this as shorthand for "Follow Friday," a weekly tradition where users recommend people that others should follow on Twitter. You'll see this on Fridays.
Using hashtags correctly
If you Tweet with a hashtag on a public account, anyone who does a search for that hashtag may find your Tweet
Don't #spam #with #hashtags. Don't over-tag a single Tweet. (Best practices recommend using no more than 2 hashtags per Tweet.)
Use hashtags only on Tweets relevant to the topic.
And if you Click on Any Hashtag it will Show you Whos Tweeting About that Particular Thing
Does The Hashtag Work With Facebook
The Hashtag Will Show up on Facebook but on From Facebook it will not link out to anything However when you View the Tweet on Twitter it Will Show
Can i Make my Own Hashtag
Yes you Can All you Got to Do is Type in # and than What Ever Name you Want to Start and you have your Own HashTag
And Anybody That Tweets About that you will Be Able to View All The Tweets That Have that Inside Them