The "Exklusive Kindle eBooks" section, as it is known on Amazon.de, offers over 500,000 ebooks which can only be found in the Kindle Store. Many of these titles are published by indie authors, including through the KDP Select program. Most (all?) of the titles are also available via the Kindle Owner's lending Library. I'm not sure Amazon intended to do so, but in adding the new section they gave Prime members an easy way to find ebooks which they can read for free.
On a related note, and I do find this a little amusing, none of the titles in the Kindle exclusive section of Kindle.de are from German publishers. Thanks to Germany's book pricing laws, it is illegal for a publisher to offer books exclusively to a particular retailer. It's not clear whether that also applies to self-published authors in Germany, but it might.