The iPhone goes to sleep by default after it�s been inactive for a certain period of time. But what if you want to actually turn off the iPhone, not just let it sleep? Or what if you want to restart it?
To do either, start by
To do this, hold the sleep/wake button and Home buttons simultaneously for a few seconds; the display will quickly wipe itself and you should see the black background and white Apple logo, signifying a reset well done.