iPhone's screen won't rotate?

When you turn your iPhone sideways, but the screen won’t rotate? Here is how to fix the problem:

1) The iPhone won’t rotate because Portrait Orientation Lock is turned on. Look in the upper right-hand corner of your iPhone’s screen, just to the left of the battery icon. If you see a tiny lock inside a circular arrow, Portrait Orientation Lock is turned on. That's why the screen won't rotate.

2) To turn off Portrait Orientation Lock, swipe up from the bottom of your Iphone's display to reveal Control Center. Tap the button with the lock inside the arrow circle Portrait Orientation Lock Button to turn Portrait Orientation Lock on or off.