Observe Mode and Control Mode disable and enable (respectively) input devices for the Mac you're connecting from with Screens. These modes are useful when you want to see the remote desktop, but don't want input from your keyboard or pointing device to interfere with activity on the remote computer. To select a mode while you are connected to a remote computer, use one of the following methods:
Click the Observe/Control button in the Screens toolbar.
Navigate the Screens application menu: View > Switch to Control/Observe Mode
This mode lets you see what is happening on the remote computer, but will disable the keyboard and mouse. You can also set Screens to use this mode automatically in the saved screen settings.
This is the default mode. Keyboard and mouse commands are sent to the remote computer as normal.