I have to admit: This message is not intuitive. It is probably not even guaranteed that every reader heard about hashtags at all. To bring us all on the same level of understanding: The social network Twitter uses so called hashtags as filter criteria. Anybody who wants to add a message to a specific topic just adds the hash (#) to a word, e.g. #myhashtag – and now the message can be found by anybody who looks for this term.