All foldable phones, regardless of whether they fold horizontally or vertically, come with two displays. The outer displays are meant to allow quick access to the device's features when the user doesn't want to unfold the device to use it, and they also offer some unique possibilities.
For example, on Samsung Galaxy foldables, you can use the cover displays as a viewfinder so you can capture photos using the rear cameras, which tend to offer considerably better quality than front cameras.
You can also put both the outer and inner screens to work at the same time. For example, when you're taking photos of a friend or family member, you can operate the camera on the inner display while the cover display can show the subject a preview so both the photographer and the subject know what the final shot will look like.
Unfortunately, while Samsung's Galaxy Z Fold and Galaxy Z Flip smartphones come with a few out-of-the-box features that use the two screens at the same time, third-party apps that support doing so are non-existent. But that is set to change with Android 14.
Android 14 supports dual display mode on foldables for third-party apps
With Android 14, Google has built in the necessary APIs that allow apps to operate in dual-display mode and use both the front (inner) and rear (cover) screens. Taking advantage of those APIs also requires OEMs to make some changes from their side, and Samsung has done so with the Android 14 update for its foldables.
It will be interesting to see what developers will be able to achieve with the official tools available in Android 14. Google already showed at least one excellent use case when it announced the Pixel Fold a few months back: Google Assistant's dual screen interpreter mode lets you speak or type text on the inner screen while showing a translated version on the outer display.
It will probably take some time for third-party apps to jump onboard. Foldables aren't exactly selling like hotcakes, and Android 14 was only recently released and has yet to make its way to most foldable smartphones. That includes Samsung's Galaxy Z Fold and Z Flip devices, for which Android 14 is still in a beta phase and will remain so for a few more weeks.