the "people" taxonomy is defined. It's defined to work for posts, and a rewrite slug is defined to make the url into '/person/' instead of '/people/'. The capabilities line is optional. Without it, WordPress will default capabilities to the same users as posts. As shown above, this will allow any user with the custom "edit_guides" capability to assign the taxonomy to a post and any user with the custom "publish_guides" capability to create new taxonomy items.