Extras and extra categories
Extras are individual options. Their form includes name, SKU, price, visible-as text, and one or more extra categories.

Extra categories control title, Accordion/Flat style, checkbox/radio/select/quantity input, minimum and maximum options, required selection, hidden prices, visible-as text, and global product categories.

Selected extras appear below the order item, in detail, and on receipts when supplied by WooCommerce.
Review product associations before deleting an extra or category.