I believe it is something called the "universial joint" that allow torque from the drive shaft transfer onto the wheel. The idea of universial joint is connecting two shafts with a special joint that allow the two shafts rotate as a whole, while the angle between the two shafts remains the same angle and direction.
Here's a simple picture of what it looks like:
http://www.tpub.com/machines/11g.htm
A universal joint is a mechanical connection between rotating shafts which are generally not in parallel, but intersecting. "U-joints" transmit torque.
Because of the two pivots on the U-join, you will be able hold onto one end of the join, then point the other end to any direction you want. So, when the steering hold the front wheel in certain angle, the universial joints are forced to adjust to a new angle when ever the drive shaft rotates.
I've seen a smaller version of U-joint from small part, so you might want to order one and look at it yourself...