New Samsung Galaxy Fold Mockup

Some Examples:

Samsung look set to unleash its feverishly-anticipated foldable flagship handset, dubbed Galaxy X or Galaxy Fold, early next year. The all-new smartphone boasts two OLED displays – a 4.5-inch screen, known as the Cover Display, and a 7.3-inch "Infinity Flex Display" which opens unfolds like the pages of a paperback to offer a fully-fledged tablet experience when playing games, and watching games.

Source : T3

The future of the fold
As for technology, the twofold is not the only way a phone can unfold. Enter a parchment fold, a clamshell fold, and a z/flyer fold concepts by Riaz Mohamed:

Future & Types of Mobile Foldable by Riaz Mohamed