Wikipedia defines tagging as follows: “A tag is a non-hierarchical keyword or term assigned to a piece of information (such as an internet bookmark, digital image, or computer file). This kind of meta data helps describe an item and allows it to be found again by browsing or searching. Tags are chosen informally and personally by the item’s creator or by its viewer, depending on the system. On a website in which many users tag many items (such as photo-sharing site Flickr), this collection of tags becomes a folksonomy.”

What’s a folksonomy? It is a collaboratively generated, open-ended system of labeling things. And because tags are user-generated by anyone wanting to label practically anything online (text, photos, video, audio files, and so on), they tend to be informal, somewhat disorganized, and often highly subjective, as well as subject to typos. I might tag an online photo of my pet “Inky”. If you didn’t know me (or him), you’d be more apt to find it if I tagged the picture as “black cat”. Similarly, “apple” might apply to a fruit, or to a personal computer. “Mouse” might be a rodent, or a computer peripheral.

See the similarities between tagging and keyword research? Tags can be viewed as a huge pool of user-generated keywords.

However when accorded a measure of strategic planning and keyword research, tagging can certainly help to boost the visibility of online content. A good example of this is the principal of organized tagging that’s been adopted by many conferences, seminars, and similar live events. Such meetings designate an official tag, which is a keyword or phrase participants are invited to use in online discussion of the event such as in blog entries, photos, and presentations. The global Search Engine Strategies Conference, for example, recently asked attendees at their annual San Jose, California, event to tag blog entries, photos, and videos with SESSJ08, so everyone who wanted to could find material related to the conference, no matter what the material or who posted it.

Search engines can index these “official” tags, which makes relevant materials related to the event searchable in a uniform way.

Blogs, particularly editorial and professional blogs, adopt lists of tags that are assigned to entries. This enables a reader to quickly search for all posts related to a specific name, product, event, service, and so on.

Del.icio.us and furl.net are websites that enable users to “tag” any web page. Del.icio.us describes itself as “a social bookmarks manager” and describes its tags as “one-word descriptors that you can assign to any bookmark”. Furl.net calls itself “a free service that saves a personal copy of any page you find on the Web, and lets you find it again instantly by searching your archive of pages. It’s your personal Web”. Because these social bookmarks and their associated tags are shared with other users of the service, it’s not a bad idea to create accounts with del.icio.us and furl.net with the appropriate tags for different pages and elements of a website.

Say your site is about cats. It might have sections about cat behavior, cat health, cat nutrition, kittens, cat toys, cat litter boxes, cat shedding, cat grooming, and cat training. All these pages or sections can be tagged in social bookmark sites such as del.icio.us and furl.net, which can help make them more visible to other users. Similarly, you might post photos of your next corporate event on Flickr or Picasa, tagging them something like “Cat & Co. Conference 2008”. You can use other tags as well, of course. Just be sure that you use at least one good, descriptive tag in every post to unify the group. And be objective. Instead of tagging a picture of yourself “me,” use your full name, and perhaps your title and company name, too.

In keeping with the social nature of Web 2.0, social sites go well beyond allowing you to tag your own content. Photo-sharing sites enable other users to browse and add their own tags to publicly viewable material, just as YouTube does with video. When developing a list of tags to use on your own content, do some research first. Check out related or categorically similar material on photo-sharing sites, video-sharing sites, social bookmark sites, and certainly in blog search engines such as Technorati. People search engine Spock.com is a good place to research tags related to individuals, running the gamut from company names and job titles to descriptors such as “red hair” and “lived in Paris.”

You’re likely using tags more often than you realize, both on the Web and on your own personal computer. iTunes, for example, encourages you to add tags such as “rock,” “alt country,” “comedy,” or “audio book” to MP3 files. Gmail invites users to categorize their mail—and hence make it more searchable—by adding tags.

Tags help make digital content more organized and searchable, albeit in the most informal fashion. Tagging is not to be sneezed at for being so unstructured. If tags can help you find your own digital media, they can help lead others to it, too.

Think back to the era of paper file systems. You may have filed your taxes under “income tax 1977” or “IRS 1040 1977”. But you tagged that file as something. If you hadn’t, you’d never again be able to lay hands on those important tax documents.

Just as a naming system worked in the era of file cabinets, tagging makes sense for a digital era, as well as for digital search.