Object Components, a subset of all Components, are used to create and render 3D scenes within TouchDesigner (also called Objects).
There are 11 object component types, with Geometry, Camera, Light and Null being most common:
Ambient Light COMP
Camera Blend COMP
Shared Mem Out COMP, Shared Mem In COMP
The component types that are used to render 3D scenes: Geometry Component contain the 3D shapes to render, plus Camera, Light, Ambient Light, Null, Bone, Handle and other component types.
The 3D data held in SOPs and passed for rendering by the Geometry COMP.