Customizing the Ubuntu GNOME Desktop Panels
From Techotopia
The bars across the top and bottom of the desktop are called panels. The top panel (shown below) contains the desktop menus and other items such as the date and time and various status indicators.
The panel along the bottom of the desktop (shown below) contains button to hide and show the currently running applications, an area for switching between workspaces, a button to hide all currently viusible application windows and an icon to open the trash can.