When the presenter shares his desktop then the attendee will be able to view the Desktop. We do not show the presenter desktop back to the presenter - since it would lead to a loop of infinite images.

When you start desktop sharing , the "bubbles icon" on the system tray will lit up as shown below in screen shot.
 




Once you stop desktop sharing, the icon will be greyed out.You can also stop desktop sharing by right clicking on the icon and select exit.