Tags are generally chosen informally and personally by the item's creator or by its viewer, depending on the system, although they may also be chosen from a controlled vocabulary. In 1997, the collaborative portal "A Description of the Equator and Some ØtherLands" produced by documenta X, Germany, used the folksonomic term Tag for its co-authors and guest authors on its Upload page. Each of those tags is usually a web link leading to an index page listing all of the posts associated with that tag.

Online communities and social computing: second international conference, OCSC 2007, held as part of HCI International 2007, Beijing, China, July 22–27, 2007: proceedings.These forms of knowledge often exist outside the data itself and are derived from personal experience, insight, or expertise. In January 2007, Aaron Straup Cope at Flickr introduced the term machine tag as an alternative name for the triple tag, adding some questions and answers on purpose, syntax, and use.

There may be some latency between the time a tag is added to a device and its availability in the devices list and device page. Proceedings of the International Conference on Weblogs and Social Media (ICWSM), Boulder, Colorado, USA, March 26–28, 2007.A Description of the Equator and Some ØtherLands", collaborative hypercinema portal, produced by documenta X, 1997. A knowledge tag is a type of meta-information that describes or defines some aspect of a piece of information (such as a document, digital image, database table, or web page). When tags or other taxonomies have further properties (or semantics) such as relationships and attributes, they constitute an ontology. A cautious partnership: the growing acceptance of folksonomy as a complement to indexing digital images and catalogs".