If you want to add tags or labels to your content, or if you want to put your content in categories, there's a module called taxonomy which does that. The module and the URLs that it generates is called "taxonomy", but in the UI, it's called "categories". That's about all there is to know...
No, actually there's one case where you don't want to use taxonomy:
- The amount of content you write is bound, like when you're writing the pages yourself (as opposed to users on the site posting content).
- You want a strict, hierarchical categorization. You want the navigational breadcrumb links to be created (and in this hierarchical way), even if you label/tag the content using taxonomy later on or in a different way.
In this case, the Drupal Way is through the menu system, potentially using a new top-level menu.
