From here you can access the ‘Multiple displays’ context menu where you can configure how Windows 10 uses the two monitors. The following operating modes are available:
Extend these displays: This option utilises both monitors to provide you with an extended desktop interface. This unified desktop is interrupted by the physical frames of the monitors themselves, however, it can be operated as a single display. For example, you can drag application windows freely from one monitor to the other.
Duplicate these displays: This option displays the same content on both monitors. This setting is particularly practical for presentations, in that it allows you to display the exact same content from your PC on another screen using a projector, for example.
Show desktop only on 1/2: This option allows you to select which monitor is to be used. The other monitor is subsequently deactivated and remains black.