https://www.cnet.com/news/galaxy-fold-mate-x-flexpai-and-more-here-are-all-the-foldable-phones-that-are-coming-apple-iphone-lg-motorola-huawei-xiaomi/

As the biggest tech company to throw its hat into the ring, many were eager to learn about the Galaxy Fold at Samsung Unpacked and it didn't disappoint. When closed, the Fold has a secondary 4.6-inch display that serves as its "cover," with all the usual features you'd expect on a phone. When you're ready for something bigger, the Fold opens up like a book to a 7.3-inch tablet.

To achieve this design with no visible line across the screen, the Fold has what the company calls an Infinity Flex Display. Essentially made out of a fancy plastic material, the screen can flex and fold hundreds of times without breaking. With the help of Google's OS, apps will switch smoothly between display sizes as well.