What's the name of the big blue screen (formerly called 'desktop')

Hi All,

When I log into F18 (and even past versions since GNOME3), I get a visually appealing blue screen. The blue screen is blank except for a title bar with 'Activities' and a hidden side bar.

I want to save items to the blue screen for convenience and quick access. I tried 'Desktop', but nothing shows up so I'm guessing its not the desktop.

What is the name of the empty blue screen?

Jeff