[Daffynition]

The way I understand it...winglets to planes are like wingtips to shoes. Both serve the same porpoise. ;D

[wita]

Not so. Major improvement in fuel efficiency and range with the addition of winglets. I will gather the facts.

http://airlineworld.wordpress.com/2008/10/01/aircraft-winglets/

final answer that I did not know:

The 747-8, the 787 and the A350 will have special, new kind of wings, which do not have a separate winglet, but have raked, and blended wingtips integrated - without a sharp angle between the wing and the winglet.