The Digital Marketer explains the history and purpose of hashtags (#).
Hashtags (#) were developed by the Twitter community of users, and not by Twitter the company. They add context to your tweets and provide some cohesiveness between many related tweets from you or from a group of Twitterers, making it easier to tag and search Twitter content. So if you're tweeting about wine and you're a woman, you might add #womenwine to your tweet. If you're participating in a Twitter chat with other small business owners, you would tag your tweet #smallbizchat so your tweet is included in the greater context of the overall chat event conversation.
Hashtags create "groupings" of tweets on Twitter but the onus is on you, the Twitterer, to add the proper hashtags. Many events these days actually supply official hashtags for the overall conference and even individual sessions. Be strategic about how you use hashtags, especially when you want to be able to track related conversations in the Twitterstream. Hashtags should not distract from the content or confuse the reader.
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