In WordPress, a taxonomy is a grouping mechanism for posts. WordPress has three built in taxonomies : categories, tags and links. WordPress allows to create your own custom taxonomies which are an extremely powerful way to group various items in all sorts of ways.
I created the custom taxonomy Family for my family blog. The WordPress plugin Custom Post Type UI, developed by Brad Williams and Michael Beckwith, is a useful tool to manage custom taxonomies.
Additional informations about WordPress taxonomies are available at the following links :
- Introducing WordPress 3 Custom Taxonomies, by Paul Kaiser
- WordPress Taxonomy Generator, by Rami Yushuvaev