Details appear to have leaked about the upcoming Nintendo NX console, saying that it is a high-powered handheld which can plug into a TV docking station, features two detachable controllers, will use cartridges and is less powerful than current-gen hardware.
Eurogamer (which claims a number of sources) says that Nintendo's pitch is simple - that you can "take your games with you on the go". That's borne out by the reported design, a high-powered handheld. Controls are attached to either side, and can be detached as two smaller controllers for use in local multiplayer. IGN has also verified this information from a separate source.