Before web applications borrowed the term tags to mean keywords about pieces of digital information, we thought of tags as something you added to a product to give a bit more information. For example, you might add a sale tag to a shirt to let everyone know its new price.
Photo tagging isn’t much different, in the sense that you’re adding keywords to a photo to let everyone know a little more about that photo (and to provide terms that people can search for to find photos of specific subjects). You can think of tagging as a way of describing your photos [Hack #10] for a larger audience, while organizing them for your own use.
Imagine you have a picture of a shirt, and you’d like to be able to find that picture in the future. If you add a few tags to the photo, such as shirt, clothes, or fashion, when you want to see that picture in the future you can simply browse your tags and view all of your photos tagged with shirt as a separate collection of photos. Also, anyone else interested in pictures of shirts will be able to see your photo as part of the larger, global collection of photos tagged with shirt.
Flickr was one of the first applications on the Web to allow tagging of content, and Flickr members have come up with many ways to use tagging to their advantage. Some have created alternate interfaces and games [Hack #11] for browsing global tag collections. Others have found a way to use tags to indicate the location a photo was taken [Hack ...