The difference between 3D rendering and 3D visualization is a matter of process. 3D visualization includes 3D rendering under its broader umbrella. 3D rendering is the final stage of the 3D visualization process, when the software combines the elements of the 3D models, 2D graphics, still images, and text into a final form.
By comparison, the larger 3D visualization effort refers to the entire process of making a 3D graphic, which can include modeling, texturing, lighting, 3D rendering, and post-production elements