The Lite Mode allows you to add an app to the main screen, a feature available with the Start screen on Windows Phone. You can change the font size and even change the direction that the main screen slides, from vertical (which is the direction that the screen slides by default) to horizontal.
The screenshots below show the Lite Mode feature on a Xiaomi Hongmi running Android 4.2.2. This is the model once known as the Red Rice that offered a phone powered by a quad-core processor for just $130. That was a great price for such an equipped handset during the summer of 2013. Other Xiaomi models will have different features and a different look for Lite Mode.
source: MIUI via WMPoweruser