Samsung has announced new display technology, which it calls Infinity Flex Display. When folded, there is what Samsung calls a Cover Display. In this orientation, the phone is pretty much like any other smartphone giving you a full touch screen in a portrait orientation.
However, if you unfold the smartphone, you're exposed to a large, tablet-sized display that gives you an incredible amount of screen real estate. According to Samsung, the display measures a full 7.3 inches when unfurled. Samsung is supporting App Continuity, which means that the app you're currently working with on the Cover Display (when folded) seamlessly transfers to the larger main display when you unfold it.
Samsung is also introducing what it calls Multi Active Window, which allows you to run three apps simultaneously on the full 7.3-inch display. Thankfully, this won't be some janky hack tacked onto the Android operating system. Samsung has worked together with Google to add native support for the Infinity Flex Display to Android and there will be APIs to add app support for App Continuity (i.e. supporting resolution changes) and Multi Active Window.
We didn't get a really good look on how the final design will look like when it debuts next year. The device was hidden in a rather thick protective case to mask its true appearance, so we'll have to reserve final judgment until production image inevitably leak onto the internet). Unfortunately, we don't have any information with regards to specs or pricing for this upcoming Galaxy phone with the Infinity Flex Display, although the latter is expected to be astronomical.
In addition to the Infinity Flex Display, Samsung also announced its One UI which will be available on the Galaxy S9, Galaxy S9+ and the Galaxy Note 9. One UI is Samsung's acknowledgement that large-screen phones can be unwieldy, so it's making tweaks to operating system to make sure that your primary points of interaction are closer to the bottom of the display where your thumbs naturally rest.
At the top of the display will be large expanses of text called the "viewing area", while you will interact with UI in the area below. Samsung says that a beta of One UI will be available in the United States later this month, while it will be available to all above-mentioned smartphones in January 2019.