The Unity desktop was first introduced in version 10.10 of the Ubuntu Netbook Edition. It became the default desktop beginning with Ubuntu 11.10. The change to Unity was prompted by a philosophical difference between Mike Shuttleworth and the GNOME team over the desktop user experience. Unity is fully compatible with Gnome applications, and still uses GTK+ for development. The window  manager for Unity is LightDM.

To optimize screen space, Unity merges a windows title and menu bars into the task bar for a maximized window. The left-side of the task bar shows the title of the current active window, while the right side of the task bar shows a series of pre-defined widgets. Following is a screen shot of a Unity desktop, with no active windows:

With no windows on the desktop, the application launcher is visible on the left side of the screen. If you slide your mouse over the word Desktop, the menu options for the Desktop appear. When you launch a maximized window, the application launcher slides out of view, and the title of the application appears in the task bar. When you place your mouse over the title, the window action icons appear on the left in reverse of the traditional order. These icons are followed by the menu options for the window. For a non-maximized window, only the title appears in the task bar, the application launcher panel remains visible, and the window action items appear on the left-side of the title bar for the window. For a non-maximized windows there is no way to access the windows menu bar.

You can either launch an application from the application launcher panel, or click on the Dash icon at the top of the application launcher panel. All active windows, including those that are minimized, appear in the launcher panel with an arrow on the left side. When you click the Dash icon, the following window appears:

This is the home window for Dash, as indicated on the bottom panel. The shortcuts on the top row are to application categories. The second row are the default applications. To view additional applications, you can either click an application category, or click the icon next to the home icon on the bottom panel (this icon is equivalent to the More Apps category). The following shows the application menu, when clicking More Apps, and selecting the Accessories filter:

At the bottom of the applications, you always get a list of suggest downloads for additional applications. When you click on an application, the system opens the window, and adds the application icon to  the application launcher, with an arrow to the right of it. Since the application launcher contains more items than fit on the screen, it will stack the lower ones. As you slide the mouse down the application launcher, it unstacks these items, and stacks those at the top.

The icon on the far right side of the task bar also launches some applications, as shown below:

The default Webcam application is Cheese, which is not part of the Live/Install ISO image. However, Unity will launch the Ubuntu Software Center application to download the missing application. This menu also includes a link to the Systems Settings application (also available via the application launcher). They System Setting application is the GNOME application, as shown below:

Unity does support four virtual workspaces. To switch workspaces, you need to slide down the application launcher panel, until the Workspace Switching icon appears. For netbook users this important, as some windows extend below the bottom of the screen. The window is not cutoff, it just appears in the virtual workspace below it. You can always switch workspaces to access the missing portion of the window. This requires double click on the workspace to make it the active workspace.

Unity is a totally different experience. It takes awhile to get used to its unique behavior.