Tagging is more commonly used in blog, where a key word is used to describe something and is attached to create a link. Other sites with identical tags are then linked together, creating a space when common topics can be categorised and fun with ease. When made public webopedia describes it as a bookmark service, creating an index.
The use of key words for identification was born before the age of the web, however it’s introduction to the web debuted and gained popularity on social media and blogging sites. There are many sources such as the reading on tags as content , describing the different tagging styles, the most common and contemporary form on social media being hash tagging, especially on social media platforms such as Instagram and Twitter.