Animation

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Reactions (Reaction Manager)
Use of one animation track to control others visually by using key positions called states.   Used for animating facial rigs etc.

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Wiring
Use of one animation track to control others through a mathematical expression so only one object needs to be animated.  Used for animating gears etc.

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Inverse Kinematics (IK)
Arranges all the elements of a hierarchical structure so that the child object aligns to an IK target.  Used for movements like using a mouse where the mouse position defines the shape of the arm.

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Forward Kinematics (FK)
How a standard hierarchical structure is animated – i.e. manipulating the base object first, then each child in turn.  Used for movements like hand waving where the objects move in arcs.

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Skinning
Defining how bones control a mesh object.  The vertices of the mesh are linked to bones using weightings so that more than one bone can influence the movement of each vertex.

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Rigging
Building some control structure for a character or object – usually using bones, supplemented with control objects and IK solvers, and sometimes with wiring or reactions too.

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