On an iPhone, when you tilt your device on its side, the screen follows and rotates to landscape orientation. Turning on portrait orientation locks the screen so that no matter which way your iPhone is turned, the screen will stay in place. Instead of your iPhone screen flipping between portrait and landscape view, you can use portrait orientation lock.
You can lock the screen orientation on your iPhone or later model of iPad quickly and easily in Control Center. If you have an iPad Pro, iPad Mini 4, or iPad Air 2, or any of the later models, you will be able to lock your iPad screen using portrait orientation in Control Center just like you do on iPhone. To do this: