They can be swapped between each window by pressing Shift + Tab. That means that Clip View will be on one display while Device View is on the other. Live can't show the Clip View or the Device View on both windows at the same time.You can of course drag the main window to any of your monitors. Live's Browser and the Info View will be shown in Live's main window.The second window can be enabled from View Menu → Second Window.
If there is only one large monitor available, the second window can be used to work with different views at the same time. When working with two monitors at the same time, you can see the Session/Arrangement and Clip/Device Views simultaneously, or dedicate a single monitor to detailed MIDI clip editing.