What happens when you put your iphone into dfu mode when its turned on?

I had my iphone on and put it into dfu mode( i think thats what its called ) but i held down the home and power button for ten seconds and then let go of the power button and continued to hold the home button for another ten seconds. My screen went black and now it won't turn on! I plugged it into itunes and restored it. Will that fix everything. If not help me please!

That's what happen to my iPhone but just do dfu mode again and it work but if not your iPhone might not turn on again you might have to get a new one