Below is a list of WordPress built in taxonomy names and built-in post type names. Never name your custom taxonomies and post types with one these to avoid collisions.
category— Categories (Posts)
post_tag— Tags (Posts)
nav_menu— Menu items (Appearance > Menus)
post_format— Post formats
attachment— Media attachments
revision— Post revisions
nav_menu_item— Menu items (Appearance > Menus)
This information can also be found in the WordPress codex, but it’s rather buried and difficult to find. Hopefully this helps anyone looking for a quick reference to the names of WordPress built in taxonomies.