Attached Link: http://www.euclideanspace.com/physics/kinematics/joints/

***"What is the true meaning of Inverse kinematics"***

You really want to know? It can get quite technical. ;-)

Here's another interesting read about motion capture and skeletal animation, which briefly touches on the importance of IK:

Siggraph Paper On Acclaim's Optical Motion Capture System

Quote: "Inverse kinematics was a great breakthrough for 3D character animation, providing a "goal-directed" approach to animating a character. It allows the artist to control a 3D character's limbs by treating them as a mechanical linkage, or kinematic chain. Control points, connected to the ends of these chains, allow the entire chain to be manipulated by a single "handle". In the case of an arm, the handle would be the hand at the end of the arm."

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.