Tags are a form of a metadata. For those unfamiliar with the term “metadata”, it is data that describes data. Like the musical genre of an album or the category a book belongs to (cooking, history, etc). Tags have greatly expanded in popularity thanks to services like Flickr and Delicious and blogging platforms like WordPress and Drupal. In the simplest terms, tags describe a piece of content and can help in searching or categorizing images, blog posts, or any other variety of data. Tags are also a form of folksonomy, a classification system built by users from the bottom up as opposed to top down categorization systems like you’d find in a physical bookstore.
A real world example of tagging would be the classification system that most bookstores employ. Books are widely categorized by their topics such as cooking, fiction, history, etc. Within those classifications, you have more specific sections such as categorizing cookbooks by cuisine or technique. While this makes browsing the tens of thousands of books in a bookstore easy, tagging like this takes on a whole new level of power in digital applications.
If you had a blog where you reviewed books that you read, you could easily apply multiple tags to a single entry. If you were to review a book on Thai vegetarian cooking, you might apply some tags such as “Thailand”, “cooking”, “Asian”, “spicy”, “vegetarian” etc. When looking at these tags on just one entry, it doesn’t provide much use. But if you have a blog that spans several hundred entries, tags become an invaluable tool for users browsing your site.
Let’s say a user lands on your latest entry about this Thai cookbook and really enjoys your review and also enjoys Thai cooking. They could click on the tag “Thailand” and would be greeted with a list of every entry that you’ve ever tagged with “Thailand”. This would even include books that might be about Thailand but not about cooking such as history books. A lot of systems give users to browse combinations of tags so they could look at all entries that were tagged as “vegetarian” and “Asian” to get an overall of all vegetarian Asian cookbooks that you’ve reviewed.
At this point, you might be wondering why a user wouldn’t simply use your site’s search engine functionality to find these items. After all, it’d be easy enough to type in and search for “Asian vegetarian” or “Thailand”. Tagging is superior to search, though, because properly chosen tags should describe the main subject of a piece of content. Search, on the other hand, could pick up a single instance of a word in a blog post and return it as relevant results.
Maybe you started one of your blog posts about a book on gardening by saying “When I was in Thailand last year, I found the most amazing gardening book” and then went on to discuss the book which has absolutely nothing to do with Thailand. Users searching for “Thailand” would find this entry which is irrelevant to the subject matter they’re searching for. However, browsing by tags would exclude this entry unless you tagged it as “Thailand”.
Not only can tags be applied to pieces of text-based content; they can also be applied to images or video or any other piece of content you can imagine. The biggest benefit of tags is that they’re chosen by a human and therefore should be more accurate. Even the best of search engines can only guess at how relevant a blog post is to the given search terms.