Flickr is a photo sharing website and web services suite, and an online community platform, which is generally considered an example of a Web 2.0 application.
In addition to being a popular Web site for users to share personal photographs, the service is widely used by bloggers as a photo repository. Its popularity has been fueled by its innovative online community tools that allow photos to be tagged and browsed by folksonomy means.
Flickr allows photo submitters to categorize their images by use of keyword "tags" (a form of metadata), which allow searchers to easily find images concerning a certain topic such as place or subject matter. Flickr provides rapid access to images tagged with the most popular keywords. Because of its support for user-generated tags, Flickr repeatedly has been cited as a prime example of effective use of folksonomy, although Thomas Vander Wal suggested Flickr is not the best example of folksonomy. Also, Flickr was one of the first websites to implement tag clouds.
Flickr also allows users to categorize their photos into "sets", or groups of photos that fall under the same heading. However, sets are more flexible than the traditional folder-based method of organizing files, as one photo can belong to many sets, or one set, or none at all (the concept is directly analogous to the better known "labels" in Google's Gmail). Flickr's "sets", then, represent a form of categorical metadata (computing) rather than a physical hierarchy.
Organizr is a web application for organizing photos within a Flickr account. It allows users to modify tags, descriptions, and set groupings, and to place photos on a world map (a feature provided in conjunction with Yahoo! Maps). It uses Ajax to closely emulate the look, feel, and quick functionality of desktop-based photo-management applications. Because of this, Organizr greatly simplifies the batch organization of photos, which is more cumbersome with the web interface.
Flickr provides both private and public image storage. A user uploading an image can set privacy controls that determine who can view the image. A photo can be flagged as either public or private. Private are visible by default only to the uploader, but they can also be marked as viewable by friends and/or family. Privacy settings also can be decided by adding photographs from a user's photostream to a "group pool". If a group is private then all the members of that group can see the photo. If a group is public then the photo becomes public as well. Flickr also provides a "contact list" which can be used to control image access for a specific set of users in a way similar to that of LiveJournal.
Many of its users allow their photos to be viewed by anyone, forming a large collaborative database of categorized photos. By default, other users can leave comments about any image they have permission to view, and in some cases can add to the list of tags associated with an image.
Flickr offers users the ability to release their images under certain common usage licenses. The licensing options primarily include the Creative Commons attribution-based and minor content-control licenses. As with "tags", the site allows easy searching of only those images that fall under a specific license.