no description available, TAbstractComposedGeometryNode description follows
no description available, TAbstractX3DGeometryNode description follows
no description available, TAbstractGeometryNode description follows
Geometry nodes are the only nodes that produces some visible results during rendering. Much of the VRML language is just a method of describing properties how geometry nodes are displayed (materials, transformations, lighting).
Only geometry nodes define something visible "in usual way" during rendering (Some other nodes in VRML / X3D are visible but in an unusual way, like Background and Fog. These nodes must be rendered in a special way — they are not affected in any usual way by the current transformation matrix etc.)
Geometry nodes are never "grouping nodes", in particular there's never a geometry node that is (direct or indirect) child of another geometry node. So there's no need to be concerned whether geometry nodes' children are included in things like [Local]BoundingBox or Triangles/VerticesCount.
Geometry nodes don't affect anything in graph traverse state. (This is important mostly for VRML 1.0, since in newer VRML / X3D "graph traverse state" is not that important.)