What is the difference btw apple real iphone and iphone clone or master copy?

Now a days some people r making fake apple iphone. I want to buy an iphone 4s and i saw some iphone clone too. So how can i be sure which one i'm buying real one or the fake one? For the record i want to buy real apple iphone. So i need to know some trick to figure it out which one is real. So that i can assure myself that i'm buying real one.

Real iphones have the best hardware out there, obviously clones don't. With a clone you also can't use the appstore.