what is portrait orientation lock

Portrait orientation lock is a feature found on mobile devices, such as the iPhone, that allows users to prevent the screen from rotating when the device is turned. This is useful when, for example, you want to read something in bed and don't want the screen to rotate as you shift position. When the portrait orientation lock is enabled, the screen will stay in the same orientation regardless of how the device is held. This feature is particularly helpful when using apps that are designed to work only in either portrait or landscape mode.