"Full display gestures" option was initially used by Apple in their iPhone X, and now Xiaomi inspired by success of this project decided to test it in their phones. Feature was added to MIUI 9 in beta version, and at this moment project is in the testing phase.
After swiping from the bottom you can go to the Home screen. When you will add to it touch of your finger on the top of screen you can go to list with recently used apps. Swiping from the left or right may allow you to change displayed page. After beta tests for beginning Xiaomi will add this feature to Xiaomi Mi MIX, Mi MIX 2, Redmi 5 and Redmi 5 Plus devices.