Volkswagen (NASDAQOTH:VWAGY) is set on world domination: The German giant aims to become the world's largest-selling automaker by 2018, and it's not kidding around.

A big part of that push involves Audi, VW's global luxury brand. In this video, Fool.com contributor John Rosevear looks at how Audi has become VW's secret profit weapon, funding the company's massive global expansion plans.