Out of the box, WordPress offers two different ways to organize Posts; Categories and Tags. The technical names for all these are taxonomies.
"What’s a taxonomy?" you may well ask. It’s simply a way of describing things. On a geography blog, for example, you might have a "Country" taxonomy, which could be filled with country names.
Categories and Tags are more generic terms that you can fill in with specific information for your site.
But what’s the difference between Categories and Tags?
Honestly, aside from a few technical details, there isn’t much of a difference at all.
Categories are hierarchical, which means terms can have a relationship to each other, like parent and child. Here’s an example: you could have a Category called Asia, and under Asia you could have categories called Viet Nam, Thailand, and Laos.
Tags are NOT hierarchical, which means there’s no relationship between them.
If you’re a developer this can have deep and significant meaning, but if you’re NOT a developer, why do you care? And which should you use? Both? It depends. First, let’s take a look at some pictures.
On the left we have the Categories, and you can see how I have countries as children of the continent. On the right, we have the same information as Tags, and you can see how the UI is presented differently.
This video is taken from the WordPress Beginner class, and explains how to add categories:
This second video is from the same class, and explains how tags work:
Categories, Tags and URLs
As mentioned in the videos above, Categories are hierarchical, and this allows us to do some SEO tricks with the URL.
In our example of Countries, the URL of the Laos Category could be /category/asia/laos/ whereas the URL of the Laos Tag will be /tag/laos/.
The Tag URL will never get any more elements. It’ll never be more than /tag/term/ whereas the Category URL could get as long as you wish. For example: /category/north-america/united-states/michigan/kent-county/grand-rapids/ for the city of Grand Rapids.
The value of these URLs is different to different people and services. One person might love being able to tell all that info about Grand Rapids from the URL, while another might hate having to type all that information.
Another advantage of multiple levels of categories is that each one has its own archive page. Based on the path we used above, we could expect /category/north-america/united-states/michigan/ to show all the counties in Michigan. If you have that, it’s perfect. If you do NOT have that, I might recommend leaving the county term out of the hierarchy.
A Summary of Categories and Tags
When you get right down to it, there isn’t much technical difference between Tags and Categories. Practically speaking, however, they can be used in some really interesting different ways to accomplish different goals.
Which one you use (or both) depends entirely upon your goals. Don’t let technology drive your goals. Make your goals drive your technology.