A film editor is a person who practices film editing by assembling separate takes into a coherent film. In making a film the editors play a dynamic and creative role.
Typically, the editor follows the screenplay as the guide for establishing the structure of the story and then uses his/her talents to assemble the various shots and takes for greater, clearer artistic effect. There are several editing stages. The film editor often starts work while shooting is still in progress, and, in the first stage of editing he or she will work alone to create an "editor's cut" of the film. It's often many times longer than the final film will be. When time permits, the editor collaborates with the director, who gives "notes" on the editors cut. The editor and director will also have seen and discussed "dailies" (raw footage shot each day) together as shooting progresses. The editor continues to refine the cut while shooting continues.
When shooting is finished, the director can then turn his or her full attention to collaborating with the editor on cutting the film. Scenes are re-ordered, removed, shortened and otherwise tweaked. Often the need arises for new scenes to be shot. After usually several weeks of long days a "director's cut" is created, though this is not to be confused with re-edits some directors have made long after a film is finished - often decades later - to their films that were, in their view, improperly edited in the final stages by the studio and its producers.
After the director's cut, the subsequent cuts are supervised by one or more producers, who represent the production company (studio) and its investors. Hence, the final cut is the one that most closely represents what the studio wants from the film and not necessarily what the director wants. Because of this, there have been several conflicts in the past between the director and the studio, sometimes leading to the use of the "Alan Smithee" credit signifying disowner ship or the aforementioned "director's cut" re-issues in subsequent years after the original theatrical releases.
Some directors are also the producers of their films, and, with the approval of the funding studio, have a much tighter grip on what makes the final cut than other directors. The most well-known example of a director who lorded over all aspects of his films, with little studio intervention, and worked completely outside of the Hollywood system is Stanley Kubrick. On the other hand, Orson Welles is an example of a director constantly dogged by studio supervision and many times had films taken from him.
Often a film editor is blamed for improper continuity. That is, cutting from a shot where the beer glass is empty to one where it is full. Continuity is, in fact, very nearly last on a film editor's list of important things to maintain. Most important are the emotional and storytelling aspects of film-making - things which are much more abstract and harder to judge - which is why films often take much longer to edit than to shoot.