(Translated by https://www.hiragana.jp/)
Apple - Full-Screen Apps - Work and play without distractions.
The Wayback Machine - https://web.archive.org/web/20110609033354/http://www.apple.com:80/macosx/whats-new/full-screen.html

Full-screen Apps

The app and nothing but the app.

For the first time, support for full-screen apps is built into OS X. So you can take apps full screen with a click and navigate between them with a gesture.

Make it big.

Systemwide support for full-screen apps means you can work and play without distractions, using every inch of your display. Everything looks great full screen, from Mail to iPhoto to Safari. And since full-screen apps use every available pixel, they make working on smaller screens more practical than ever.

Go full screen. And back again.

Say you like to work with Pages documents in full-screen view. But you prefer to keep iCal in a desktop window. You can have it both ways. Any app with full-screen capability has a full-screen button in the top right of the app window. Just click it and the app fills the screen. Click the button again to bring the app back to the desktop.

Go full screen.

Click the full-screen button at the top right of the app window to go full screen.

Work full screen.

Your app expands to give you a completely immersive experience.

Go back.

Click the full-screen button again to return to the standard-size window.

More of the apps you love.

OS X Lion turns Dashboard into a full-screen app that’s easy to get to and a pleasure to view. Mail, iCal, Safari, Photo Booth, FaceTime, Preview, and other built-in apps come with full-screen capability. And apps like iPhoto, iMovie, GarageBand, Keynote, Pages, and Numbers were designed to work even better in full-screen view. So you can go big with just about everything on your Mac.

Some features are available only with applications developed to work with OS X Lion.