Tags enable you to associate groups of images or other files together, and associate them with items in the database.
For example, suppose you have an article on hawks in the database, and you have several pictures of hawks. By applying a “hawk” tag to all of the image files and to the article, you associate them all together.
With this association established, you can then easily create a photo gallery of all photos associated with the article.
Note that tags are not intended for organizing database content; categories and item types are designed for that task.