While you’ll very seldom face issues that will require you to reboot your iOS device, it’s good to know the option is available to you if the need arises.
If your iOS device becomes unresponsive, appears to lock up, and won’t respond to the Home Button, do the following.
Hold down the Power Button (on top of the iPad, and iPhone 5 and older devices, and on the right side of the device on iPhone 6 and 6 Plus devices). While holding down the Power Button, also press the Home Button.
Hold down these two buttons until your device’s screen clears, and a silver Apple logo appears, as seen above. Release the buttons. In a few moments, your iPhone or iPad lock screen will appear. Your iOS device should now work properly.