2-link 3-link rear suspension?

What does 2-link and 3-link rear suspension mean? I did some digging around in some books I have but they dont really spell it out clear for you.

If any one feels like lobbing this one it would be greatly appreciated

Thanks

 

Two links are like a GM truck arm. There is no articulation at the axle with the arms mounted solid to the axle, preventing axle wrap up. It's all done at the front of the arms and at the panhard bar. Two links.
A three link has three independent links, though the panhard would technically be a fourth. Common nomenclature forgets the panhard bar from here up. It uses two links for thrust, the lower trailing arms, then it uses a third for controling axle wrap. There is still a need for panhard bar or watts link for lateral location.
A four link uses the same two lower links, but adds a second on top to make axle control more predictable. A panhard is needed unless two of the links are angled to triangulate the axle with the other two links, this preventing lateral movement.