This option will not be used in 99.9% cases. But in order to bring everything to perfection it can be used.
ESI enables caching of parts of a page. Let's say you cache a shortcode for example so "Similar posts" can be cached even though the rest of the page isn't being served from the cache.
Another example is that wp-admin is not cached for the admin, but let's say the Admin Bar can be displayed from the cache.
ESI Nonces: allows you to automatically cache chunks via nonce. Add nonce to enable it. Of course, you first need to enable ESI in the first field.
