he hashtag, that ubiquitous pound sign followed by a keyword, are part of the language of social media.”- Neil Patel, Forbes
In August 2007, Chris Messina introduced hashtags (#) into Twitter’s code, which meant anyone using the platform could add a # sign front of any word(s) without spaces to make it a clickable link leading to a page where all tweets with this hashtag were aggregated. Hashtags are now used on other social media sites, like Facebook, Instagram, and GooglePlus.
Via Marta Torán
El "Hashtag": Una herramienta para compartir y aprender.