Having recently set up WordPress blogs for some clients, the question has come up:
What’s the difference between categories and tags?
I like the answer offered by Lorelle VanFossen:
I think of categories as a table of contents and tags as the index page of a book.
Use the innate structural and hierarchical characteristics of WordPress categories to organize your blog posts.
Employ a one-to-many relationship between categories and posts. That is, one post is associated with one and only one category. Although WordPress doesn’t technically limit you to treating categories as mutually exclusive, it makes logical sense to do so.
Start out with few categories — or just one. After you’ve created a whole bunch of posts, new categories may reveal themselves to you. (By default, WordPress will assign a post to a category. The default name for the default category is “Uncategorized” — not so good. Simply change that name to something like “General” or “My Blog” if you’re starting out with only one category.)
Tags are unstructured; thus, a single post can have multiple tags, and a single tag can (actually should) be associated with multiple posts.
Let’s suppose you’re an IT technician and you want to blog about professional issues as well as personal ones. If so, you could create two categories: Work and Play.
Last weekend, you (you’re still the IT technician) Skyped with your mother-in-law in Wasilla, Alaska. She took her laptop out on the porch and pointed the WebCam to Russia. Now you want to blog about the experience. Put it in the Play category, and give it the tag “Skype” (and perhaps “International Relations”).
If next week you’re going to publish a blog entry on How to Troubleshoot Audio Problems with Skype Video, put that in the Work, and give it the tag “Skype”. (And then send me the link, please.)
With WordPress, you are technically able to use categories and tags almost interchangeably. (The one major exception is that categories can have subcategories, while tags cannot have sub-tags.) But you’ll help your readers stay grounded if you use categories sparingly and tags liberally.