Auto rotate screen
This setting controls whether the screen will automatically rotate between portrait (vertical) and landscape (horizontal) layouts depends in which way up the device is held.
If this is turned off, the screen will be fixed in a certain orientation. For phones, this will be portrait (vertical) mode.
An important thing to note is that the auto-rotation feature is dependent on support in each individual app: some apps will support it, while other apps will be fixed in a portrait or landscape mode and will not rotate. Notably, on most smartphones the home screensoften do not support auto-rotation, and will only work in the portrait (vertical) mode.
Apps such as email and Internet usually do support auto-rotation.