The movies we watch nowadays are more advanced than what they used to be. The regular improvement of technology has allowed the filmmakers to literally create anything they would like to. those technological advancements allow the usage of computer graphics making something feasible.
Nearly every film being made in recent times have these special effects on them. Computer generated pictures or CGI is the not unusual time period used for the technology used in those films. How else did you believe Avatar, Transformers, all of the superhero films are made? They massively depend on CGI. And trust me, the before and after pictures will make you baffled.
The technique, if explained in popular terms could be as such. Actors should act in the front of either green or blue screen with props and technical gadgets. once the shooting part is finished, these raw motion pictures are then processed in computers have been a programmer provides layers of special effects. The before and after photographs of almost every film is present on Youtube, you could easily see them. those computer-generated photos take hours or maybe days and months to create.