https://www.cnet.com/news/mate-x-huaweis-2600-5g-foldable-phone-with-three-screens-feels-like/

Foldable phones present a chance to shake up a coasting industry while also effectively doubling the amount of screen space you have to use on your phone. Because foldable phones are phone-tablet hybrids, they can command a higher price, which opens up an important revenue stream at the top end for companies looking to make a greater profit in a slowing market. But this new era of bendable screens also represents the wild west of phone design: A phone could fold inward or outward, down the center or on two sides, or even bend back around your wrist like a watch. At this early stage, companies are working out what a foldable phone means. Right now, anything goes.

Huawei's vision for the Mate X is of a phone you mostly use in its "closed" position, but open up when you want to be entertained or more productive. There's a screen on the back that could be useful for taking selfies: The phone's four rear cameras have been codesigned with Leica.