Motion graphics are generally short pieces of visual media which combine film and graphic design. This can be accomplished by incorporating 2D and 3D animation, video, film, typography, illustration, photography, and music.
Visual effects is the various process by which imagery is created and manipulated outside the context of a live action shot. Visual effects involve the integration of live-action footage and generated imagery to create environments which look realistic, but would be dangerous, expensive, impractical, or simply impossible to capture on film.
Previs is a collaborative process that generates preliminary versions of shots or sequences, predominantly using 3D animation tools and a virtual environment. It enables filmmakers to visually explore creative ideas, plan technical solutions, and communicate a shared vision for efficient production.