Tagging is Web 2.0's answer to cataloging. Basically, you assign a word or term that you think is important to whatever item you want to find again, like a website or a picture. This is particularly helpful when you've accumulated a big list of pictures and want find all the pictures of your pet porcupine Prickly. You can tag those pictures "porcupine" or "Prickly" or "pet" or whatever term is meaningful to you.
Tagging becomes pretty cool when you can share your tags with other people, such as on the website
LibraryThing. You can see if other people have used the same tags as you, or if they have better tags. This social aspect of tagging ties into the concept of Web 2.0, where people can share information and even create information together.
Some libraries are joining the tagging bandwagon, such as UK Libraries with their
Encore interface or the
Ann Arbor District Library, which allows its patrons to tag materials in the catalog.
I think this is all very cool, even if some librarians don't. Some catalogers are decrying tagging, saying it is akin to letting a bunch of typing monkeys go wild in the world of information, which should be carefully organized and categorized just
so. I think they're missing the point of tagging. It's just another form of organization, albeit a much more relaxed one.
Besides, I think the popularity of tagging should be a clue that users don't find much use for the standard library catalog (what do you expect if the standard subject heading is "cookery" not "cooking"?), which is static in comparison to the dynamics of the web. I'm not advocating the abolishment of subject headings (they're still quite helpful for researchers), rather pointing to the need for libraries to evolve and take advantage of new technology.