What is Folksonomy?

The term was coined by Thomas Vander Wal in 2004. According to Thomas Vander Wal, folksonomy is "the result of personal free tagging of information [...] for one's own retrieval". This term became popular as part of social software applications, for example, as social bookmarking that help people classify and find information quickly using shared tags.

So, folksonomy is the system according to which users apply tags to online items to ease the search of those items. It can become a classification system based on those tags. On the contrary, taxonomy is created by owners of the content.