How does parallelogram steering work?
When you turn the wheel a gear in the steering gearbox turns a lever called a pitman arm. The pitman arm is connected to a central rod which is connected to another pivoting lever called the idler arm. The pitman arm connects (in the other direction) to a tie rod, which turns one wheel. The idler arm connects to the other tie rod which turns the other wheel. The pitman arm and idler arm always move parallel to each other, hence the name parallelogram steering. A look at an image of the system would probably help you to understand how it works.
