The humble # hashtag has completed 13 on the twitter in August. An average of 125 million hashtags are tweeted each day. In fact the makers of Twitter had not even added the hashtag feature as it was thought it to be too nerdy for common people.
Hashtag was used earlier in c-language in the file header to include external file often present in the library. For example there is a library of files called header files which are readymade pieces of software to be used in the present program.
It was the users who discovered that tweeting a term with # as prefix makes the term a clickable link. This way, not only does the post get categorised under a certain topic, it also becomes searchable.
Clicking the tag shows users all the tweets containing the tag, making it easier to follow a discussion. In tech parlance, such public tagging is called “folksonomy” which is defined as “a user-generated system of classifying and organizing online content into different categories by the use of metadata such as electronic tags such as hashtag”