
Multipane apps are enabling a tablet-like experience on smartphones. This is done through touch-enabled functions that are activated from one touch screen, with results displayed on the other touch screen.
Multipane smartphones allow apps that ordinarily take over the entire screen to also spread out functions across dual touch screens, creating a tabletlike experience on dual screen smartphones. Sprint started the trend when it introducing the world's first dual touch-screen smartphone, Kyocera's Echo, whose second screen slides out on a patented hinge.

Apps can use both screens over-under like a tiny laptop--using the lower screen for a virtual keyboard and the top one as the display. Recently, Sony announced a similar dual touch-screen smartphone called the S2, whose two screens also make it resemble a tiny laptop.
Further Reading