A neologism combining "folk" and "taxonomy", refers to collaborative efforts to organize information on the Internet. More colloquially, this refers to a group of people cooperating spontaneously to organize information into categories. In contrast to formal classification methods, this phenomenon typically only arises in non-hierarchical communities, such as public websites. Instead of using a centralized form of classification, users are encouraged to assign freely chosen keywords, typically referred to as "tags", to pieces of information or data, a process known as "tagging". Examples of web services that use tagging include those designed to allow users to publish and share photographs, personal libraries, bookmarks, social software and most blog software, permitting authors to assign tags to each entry.
The categories arising from the tagging system on del.icio.us is an example of a folksonomy. For that matter, so are the tags here on UD.