MODELING: it's the building up of the 3D object, when it's done this object is also called mesh, or wire frame, usually the three orthogonal views of the objects (blue prints) are needed to proceed to the modeling, but sometimes it is possible even without precise informations, depending on the kind of subject.

TEXTURING: it's the creation of the skin of the object, giving the right materials and textures to each single part.
Here the quality of these textures can really make the difference to the end product, in other words, however good is the 3D model mesh, if you don't dress it up with very good textures and materials, it would never work.

LIGHTING: it's the delicate stage where we create all the lights to light up the scene. There are many setting controls and several kind of lights to achieve the desired result.

Any different kind of subject, need a different kind of lighting, which is carefully studied.

This part of the work also can make the difference to the final product.

RENDERING: it's the production of the image, after we built, textured and lit the objects and the scene, we let the computer calculate the image. Usually, before we reach the final desired result, several tests are needed. Here the power of the computer processors it's very important, to reduce the timing.

ANIMATION: Theoretically, it's possible to animate any subject and scene, although there are some differences in the organization of the work, exactly how it happens on a photographic set, compare to a commercial, or a movie set.
Usually on the animation frames it's not necessary to have a very high detail, as when the image moves, not all details are appreciable, whilst for the stills, any little thing it's captured by the eye and so, here all details need to be made very carefully.

  WHY USE THE 3D WAY

There are several advantages and sensible reasons why choosing this image production method, I would list just a few of them: 

No needs to have the physical objects, this is even more important when we need to show a prototype not yet physically produced.

But also in any other case, 3D rendering can be very competitive to photography as well, considering that there are no limits to the realism achievable.

No needs of large pose rooms, or expensive cameras and lights equipments, or complex locations.

Clients can ask for changes during the work progress until the very last stage without additional costs.

Even after production, any kind of changes are possible with minimal additional costs.

The average production times and costs, are usually lower than with any other conventional method.

When more than one view of the same subject, should be shown in different positions, or conditions, the 3D way  becomes almost a must, as it's possible to amortize the cost of the modeling part, spread over all images.

Not to mention in case of animation...