Shape can appear under any grouping node. Shape can contain an Appearance node and a geometry node (for example one of the primitives Box Cone Cylinder Sphere Text, one of ElevationGrid Extrusion IndexedFaceSet IndexedLineSet LineSet PointSet, or one of the other geometry nodes). Wikipedia: see Shape.

X3D Tooltips of interest: Shape.

X3D Specification sections of interest: 12 Shape component, 12.2 Concepts and 12.4.5 Shape.

X3D Examples Archives of related interest:

• VRML 2 Sourcebook:  Chapter 03 Shapes
• X3D for Web Authors: Chapter 02 Geometry Primitives

This viewpoint slideshow is online at
https://www.web3d.org/x3d/content/examples/ConformanceNist/Geometry/Shape/viewpointSlideshow.html

Viewpoint image version history at
https://sourceforge.net/p/x3d/code/HEAD/tree/www.web3d.org/x3d/content/examples/ConformanceNist/Geometry/Shape/_viewpoints