The Translation (Hidden) content type links a translated page to its English version. It also triggers a banner on Google Translate.
When to use
This content type is only used on pages that are human-translated versions of English language pages. Use Translation (Hidden) on the Spanish, Hmong, Somali, and other language versions.
It is a way of pointing the translated page back to its English source page. The "Original English Content ID" field requires the ID of the English language page that is being translated.