This type has real footage only, no 3D. You can choose to have actors or not.
This type of film is an excellent choice for a teaser or a tight budget, given that the plot isn’t too complex or includes pricy actors.

3D animation
This type features 3D only, no real footage and no actors. A pure animation is a good choice if you want to take freedoms regarding camera angles and movements that would be costly or impossible with real physical equipment.

Side by Side
This type has both 3D and real footage but without being merged into single shots. You may or may not have actors in your real footage. This type is ideal if you want to combine the advantages of the previous formats and if you need to show an object that isn’t yet built and want to feature some of the real life surrounding the object.

This type features 3D merged into real footage (and the other way around). You may or may not add actors. This type is usually the most complex but gives you all the advantages of the previous three types. Embed your 3D into real environments, tell a story where real film and 3D are merging so that you can’t tell what’s real and what’s not and have actors move around your 3D object.