One popular iPhone feature is the ability to automatically rotate the iPhone's screen orientation depending on how the phone is held. This feature can become disabled, either intentionally or accidentally. When screen rotation is disabled, the iPhone's screen is locked in place and will not rotate when the iPhone is held at different angles. You can easily fix this problem using the iPhone's Control Center.
Starting on any screen, swipe up from the very bottom of the iPhone's display. Start with your finger below the screen and move it up into the lit display. Your finger will drag the Control Center into view.
Look for the screen rotation button at the top right of the Control Center. If the rotation is locked, it will appear illuminated in white.
Tap the icon. You'll briefly see a message that says that the orientation lock is off. This immediately enables screen rotation, allowing your iPhone screen to rotate as you hold it at different angles.
Unless you have the new iPhone 6, the Home screen does not rotate into landscape mode when you turn the phone -- screen rotation only affects some apps and video.