A grassroots phenomenon whereby users label Web sites with descriptive tags, building a network of knowledge dubbed folksonomy -- a taxonomy of knowledge organized by ordinary folk. Yahoo! was quick to spot this trend, as are other Web sites linked to below.
The term "tag" has evolved to refer to content that identifies a particular image or file, to be used in conjunction with other images or files of the same tag. On some Web sites, communities have formed around particular tags, for example: the tag "memorymaps" refers to digital scrapbooks that make use of the
ability to annotate photographs with boxes (which display pop-up captions when the mouse pointer rolls over them). Starting with a satellite image of a city or town, users attach captions to places of particular significance, for example old school friends' houses or high school hangouts. Other communities sprinkle maps with restaurants, cinemas, and other places of interest. Hey, people are into it!
Basically it is an intelligent method and tool for browsing and sharing the best Web sites.