The Inverse-Bind matrix, also known as the bone-offset matrix. Transforming a vertex by this matrix will take it from its bind position in model space and move it to the bone space for this bone so that it can be animated by the current transformation matrix for the same bone. This can be visualized by thinking of a point in the hand of a model in its bind pose. This matrix will transform that point all the way up the arm and down the torso to the hip root, or wherever you have rooted your model. Then you can multiply the point back out to where you want it using the current hand matrix (multiplied all the way from the root) for whatever frame you are on in your animation.

public Matrix InverseBindMatrix { get; set; }

Public Property InverseBindMatrix As Matrix

public:
property Matrix^ InverseBindMatrix {
	Matrix^ get ();
	void set (Matrix^ value);
}