On Flickr, you can choose to make your photos either public or private (but more than 80 percent of the 5.5 million photos are public.) You can annotate your pictures, adding captions within the frame, or post comments below other users? photos. Most significantly, you can append "tags," adjectives that describe the photo?s category (such as "dog," "poodle," "cute"). Then all of the photos that share a particular tag can themselves be explored as a group, which online pundits call a "folksonomy."