How to restart
Press and hold the Sleep/Wake button on the top of your device until the red slider appears. Then drag the slider to turn your device completely off.
After the device turns off, press and hold the Sleep/Wake button again until you see the Apple logo.
How to reset
You should reset your device as a last resort and only if you can't restart it.
To reset, press and hold both the Sleep/Wake and Home buttons for at least 10 seconds, until you see the Apple logo.