Film editing is part of post-production, or everything that goes on after the actual shooting of the film stops. Other aspects of post-production include sound editing and mixing, computer generated effects, and soundtrack creation. The film editor’s job is to join together the various shots into scenes, and the scenes into a finished movie. They usually work closely with the director to realize his or her vision for the film and to make the efforts of everyone else involved shine.
Before the advent of digital editing, the film editor would literally cut up the film and piece it back together. An editor would take long strips of film, cut them precisely, and stick them to other strips with tape and glue, creating rolls of film. Nowadays, all this work is done on a computer and is much more accessible to amateurs.