For example, let’s say a remote Mac has two user accounts—Joe and Jane. Joe is currently working on that Mac in his account. From another Mac, Jane can select that Mac under the Shared heading in a Finder window, click Share Screen, and enter her user name and password in the resulting dialog box. When she clicks the Connect button, a Select Display window appears. Within this window are two options—Ask to Share the Display and Connect to a Virtual Display. If she clicks Ask to Share the Display a message appears on the other Mac indicating that Jane would like to share the screen. If Joe clicks Share Screen, Jane can see what’s on Joe’s screen as well as control Joe’s account.
Okay, that is very cool.