Most films today use visual effects. Visual effects (VFX) offers lots of ways to create some great scenes in movies. The use of visual effects allows film companies to create something in a movie that may not be possible to do in real life. Visual effects are also used to create the background of the scene as the scene may take place in somewhere that is difficult to film in like a scene in the middle of New York City or a popular tourist destination. Also, visual effects are uses to create characters or another living anima that would be impossible to create in real life just like the dinosaurs in Jurassic Park.
Below are 3 videos showing the use of visual effects and how they work:
Level 2 Games Design 