Folksonomy is collaborative tagging and method of collaboratively creating and managing tags to annotate and categorize content. In it metadata is generated not only by experts but also by creators and consumers of the content.
Folksonomies arise in Web-based communities where provisions are made at the site level for creating and using tags. These communities are established to enable Web users to label and share user-generated content, such as photographs, or to collaboratively label existing content, such as Web sites, books, works in the scientific and scholarly literatures, and blog entries.
A folksonomy begins with tagging. On the Website Flickr.com, for example, users post their photos and label them with descriptive words. You might tag the picture of your cat, "cat," "Sparky" and "living room." Then you'll be able to retrieve that photo when you're searching for the cute shot of Sparky lounging on the couch. If you open your photos and tags to others, as many Flickr devotees do, other people can examine and label your photos. A furniture aficionado might add the tag "Mitchell Gold sofa," which means that he and others looking for images of this particular kind of couch could find your photo. "People aren't really categorizing information," Vander Wal says. "They're throwing words out there for their own use." But the cumulative force of all the individual tags can produce a bottom-up, self-organized system for classifying mountains of digital material.
Folksonomy may hold the key to developing a Semantic Web - web 3.0, in which every Web page contains machine-readable metadata that describes its content. Such metadata would dramatically improve the precision (the percentage of relevant documents) in search engine retrieval lists.