As you might have noticed, I've just recently implemented a tag setup on this blog. See the tags down there in the byline, between the categories and trackbacks? Yup, there they are. Tags. So what are tags and how are they different from categories?
Tags are meta data. They're a way to mark posts (and sometimes other types of information) with keywords. If you think that sounds a lot like what post categories do, you're both right and wrong. Categories are similar, but there are important differences.
Categories are a general catch-all for any post that fits a certain criteria, even if those posts have key differences. For example, I use my Geekery category for any post about technology, the web or blogging and all its minutiae. But a post about WordPress will have little in common with a post about Firefox. So in this single narrow sense, tags allow me to use keywords to identify the real subject of a post rather than a broad generalization.
Further, my tag implementation allows archive-style views of all posts bearing any given tag. Try it out, click on one of them. At first glance, this seems pretty similar to WP's built-in search function. Here again there are key differences. If you search for "Firefox," this post will appear in the results. But just because I mentioned Firefox doesn't mean the post is about Firefox. And then there are some posts that don't clearly state their subject, like this photo post. Search for "Pope Benedict" and you won't find that post because those words never appear in that post, yet the fact that he's the subject of the post is undeniable. Enter tags to fill the gap.
Tags also serve an important role in SEO. Tags can make it easier for search engines and content indices like Technorati to determine what my content is about, just as they do for human readers. Technorati in particular loves anything marked rel="tag". Now if only Technorati would start refreshing my content when I ping, I'd be all set.
So if tags are so neat, cool and interesting, why bother with categories? I feel there's room for both. Like I said, categories are general catch-alls. Those are still very useful. For example, tags or not, I'm still going to want to store all my haiku under the same roof regardless of their subject. The same holds true for things like my snippets of conversation and silly photo posts.
The way I see it there's room for categories, tags and search to fit comfortably all in the same scheme. Now if you'll excuse me for a month or so, I have a thousand archived posts to tag.
