Questions concerning the integrated gyroscope sensor. For issues with auto-rotation, please use the 'auto-rotation' tag instead.
Thanks to built-in sensors, Android is capable of many things. In this case, it's the built-in gyroscope, which can determine the device's orientation and act on movements. So the screen can adjust its orientation automatically depending on how you hold the device, from landscape to portrait and vice-versa -- even if you hold your device head down (see: auto-rotation). Other things making use of this include several games, AR apps, compasses, and more.