Hashtag
A hashtag is a word or series of words preceded by a hash tag (#). Example: #marketing terms. Hashtags are used in social media like Twitter to "tag" posts so that they can be more easily found through the internal search function. For example, it is possible to track all tweets about a TV broadcast, event or news event.
Hashtags have become familiar to the general public thanks to Twitter. They have their origins in the IRC chat networks. Other social networks, such as Instagram, Facebook and YouTube, also offer features around hashtags in status updates.