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 impossible to capture on film. Visual effects using computer generated imagery have recently become accessible to the independent filmmaker with the introduction of affordable and easy-to-use animation and compositing software.

1. 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 impossible to capture on film. Visual
effects using computer generated imagery have recently become
accessible to the independent filmmaker with the introduction of affordable
and easy-to-use animation and compositing software.

2. Compositing is the combining of visual elements from separate sources
into single images, often to create the illusion that all those elements are
parts of the same scene. Live-action shooting for compositing is variously
called "chroma key", "blue screen", "green screen" and other names.
Today,

3. A matte painting is a painted representation of a landscape, set, or distant
location that allows filmmakers to create the illusion of an environment that
is not present at the filming location. Historically, matte painters and film
technicians have used various techniques to combine a matte-painted
image with live-action footage.

4. Special effects (often abbreviated as SFX, SPFX, or simply FX) are
illusions or visual tricks used in the film, television, theatre, video game,
and simulator industries to simulate the imagined events in
a story or virtual world.

5. http://www.hitechanimation.com/
Source : Google