Categories can be organized in a hierarchical tree structure, where parent categories can have multiple levels of nested subcategories. Items can be assigned to a single category within this tree, regardless of whether it's a top-level parent category or a nested subcategory.
Tags are not hierarchical. An Item can be assigned up to 10 tags (it should be noted that Tags are essentially the same as the original ‘Categories’ employed in previous versions of the system, and indeed if you had defined Categories these will be automatically represented as Tags).
