If you've spent any time on Twitter, you've probably seen a hashtag before. A "#" symbol sets off a hashtag.
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Here's a look at how to utilize Hashtags to organize information that you contribute and consume on Twitter. As the tweets pile up, the extra time you take to thoughtfully categorize your tweets with a hashtag will help the greater Twitter community (and you individually) make the most of the service.
Twitter (the company) didn't create hashtags. The to add context to tweets. The tag would also help filter and sort them out for future readers.