What is this tag based search called?

1. What is tag based search?
2. What is an example of tagging?
3. What is tagging used for?

What is tag based search?

Tag-based systems are used by millions of web users to tag, save and share items. User-defined tags, however, are so variable in quality that searching on these tags alone is unsatisfactory. One way to improve search in bookmarking systems is by adding more metadata to the user-created tags to enhance tag quality.

What is an example of tagging?

Tags are markers used to label Internet content with additional information. They're used in different ways, depending on the context and the particular channel. For example, blog posts or posts including photos on social media channels like Facebook and Twitter can all be tagged.

What is tagging used for?

People use tags to aid classification, mark ownership, note boundaries, and indicate online identity. Tags may take the form of words, images, or other identifying marks. An analogous example of tags in the physical world is museum object tagging.