Hashtags are used in tweets from Twitter and are placed before the tag content. They mark a word or string of characters. The hash itself is followed by a letter- digit creation that must not be interrupted by a space, punctuation, or special character. Example: #greatconcert.
Hashtags are used as meta information or comments and are used in social networks for keywording. They are inserted into the body text, make it easier to find specific content and can provide references to events or be used for third-party comments.