https://www.cnet.com/news/our-first-look-at-samsungs-foldable-phone-raises-more-questions-than-answers/

Samsung isn't alone in pursuing a foldable phone. LG and Huawei are developing prototypes of their own, and one brand, Royole, has already come out with the all-plastic FlexPai, whose screen folds outward, rather than inward like the phone Samsung's Dennison showed on-stage. 

Samsung coyly refused to share more than the basics. We know that the screen bends inward like a book, and that there's a screen on the outside as well, so you can use the phone while it's folded in half. The company also detailed how it had to create some new manufacturing processes and components. Finally, we know that it uses a new interface that will run on top of Android, called One UI, which will also come to future Samsung phones, likely the Galaxy S10.