"Hashtags, once your phone’s pound sign, now have a place on most popular social networks, including Twitter, Facebook, Google+, Instagram, Vine and Pinterest. The hashtag is likely the most popular means of categorizing content on social media. It makes your own content discoverable and allows you to find relevant content from other people and businesses. The hashtag also allows you to connect with and engage other social media users based on a common theme or interest."
Are you clueless when it comes to hashtags? Could you use a few pointers about their proper use? This article from Hootsuite's blog does a great job of laying out some of the major do's and don'ts of hashtag use: How To Use Hashtags.