If you wish to record your iPhone’s screen, go to Settings > Control Center and include Screen Recording in Control Center. Then open the Control Center (to do this, on iPhone with Face ID, swipe down from the top right; on models with a home button, swipe up from the bottom) and press the button that shows a screen recording icon. Please note that a three-second countdown will take place before recording. In order to stop, you have to touch the red status bar or time bar, a confirmation step to stop the recording will follow. This video is going to be available in your Photos gallery.