When in your pocket the phone is the same as it always was: an Android device. But when the connected to a monitor (by way of a nifty looking dock) it launches into a fully fledged Ubuntu desktop running the Unity interface.
Both OSes share the same kernel – so this isn’t a case of an ‘Ubuntu’ app running atop Android or vice versa. Both run at the same time on the same device. The net result of this is a super efficient workflow.
With the smartphone already crowded as it is, I wonder how Ubuntu for Android will successfully implement the nice features found on the traditional desktop environment and cleanly transpose the system into a dual-booted Android devices. For me, I will still stay with Android. Good luck to Canonical!