I am frequently asked what the “#” symbol means when proceeding words like Public Relations, Social Media or NY Yankees. The # symbol you see throughout social media sites like Twitter is called a Hashtag. A Hashtag is a tag (or keyword) embedded in a message posted on Twitter, consisting of a word or phrase prefixed with a hash sign. (i.e #publicrelations, #socialmedia, #NYyankees). Hashtags are used to categorize tweets so that they are seen easily when an end-user enters a Twitter Search. When clicking on the hashtag you are able to view all of the tweets that include that same tag. This makes searching a specific topic easy! See below for some examples of how public relations and marketing professionals are using hashtags on Twitter.
Hashtags can be placed anywhere in a tweet and can even be used for fun and trending sayings, topics or events. A word to the wise, be careful not to go overboard with hashtags. I would recommend using no more then 3 hashtags in a single tweet. You want to avoid your tweet resembling Spam. For additional information and best practices visit the Twitter Fan Wiki on Hastags.