How is the SKU shown on a frontend product view?

Block class: https://github.com/magento/magento2/blob/2335247d4ae2dc1e0728ee73022b0a244ccd7f4c/app/code/Magento/Catalog/Block/Product/View/Description.php

Template: https://github.com/magento/magento2/blob/2335247d4ae2dc1e0728ee73022b0a244ccd7f4c/app/code/Magento/Catalog/view/frontend/templates/product/view/attribute.phtml