One of the most common cases for orientation changes is when you want to revise the layout of your content based on the orientation of the device. For example, perhaps you want a button bar to stretch along the longest dimension of the device's display. By using a media query, you can do this easily and automatically.

Why does my screen orientation keeps changing?

Some display drivers support screen auto-rotation. You may need to enable the Lock rotation of this display in Settings > System > Display. Also, try disabling the Tablet mode by selecting Use desktop mode in Settings > System > Tablet mode.

Why does my phone change from portrait to landscape?

Rotate your phone to change the screen orientation (if Auto Rotate is enabled). If Auto Rotate is enabled, your phone's screen will automatically flip to portrait mode when you are holding it upright. When you are holding it horizontally, it will automatically switch to Landscape mode.