A hashtag is a keyword or short phrase preceded by the pound sign (#) in a social post (Tweet, Facebook post, etc.).
It is a metadata tag that facilitates the grouping and searching of messages according to topics. By clicking on a hashtag it is possible to access other messages categorized on that topic.
At first, hashtags have been used on Twitter and afterwards adopted and integrated by other social media platforms.
From a marketing point of view, hashtag usage is very important as it may allows marketers to gain visibility for their promotional tweets. Marketers may directly use hashtags for their messages and also entice consumers to use them.
For more details about marketing usage of hashtags see:
TV commercial hashtag
# ad hashtag->3929]