A bone defines the subset of the geometry's control point, and defined blend weight for each control point. The Bone object cannot be used directly, a SkinDeformer instance is used to deform the geometry, and SkinDeformer comes with a set of bones, each bone linked to a node. NOTE: A control point of a geometry can be bounded to more than one Bones.
A MorphTargetChannel is used by MorphTargetDeformer to organize the target geometries. Some file formats like FBX support multiple channels in parallel.
MorphTargetDeformer provides per-vertex animation. MorphTargetDeformer organize all targets via MorphTargetChannel, each channel can organize multiple targets. A common use of morph target deformer is to apply facial expression to a character. More details can be found at https://en.wikipedia.org/wiki/Morph_target_animation
A skin deformer contains multiple bones to work, each bone blends a part of the geometry by control point's weights.