View in HD at http://macmost.com/e-1715. Hashtags are a way of tagging posts and images on social media. They are used heavily on Twitter, Instagram and other services. You can search for posts by hashtag, and use them in your own posts. You don't need to do anything special to create a hashtag, just start using it. Sometimes hashtags are used to express an emotion or something more complex to put an ambiguous post into context, or just for humorous effect.