The basic you need to know about this term…
In the business of film production, the designation of "director" is a somewhat enigmatic title. Comparatively speaking, most of the other principal creative personnel involved in film-making hold titles that give a fairly clear indication of their professional responsibilities. Generally, one individual is responsible for overseeing the labour that is relevant to a single facet of production, whether it be cinematography, writing, editing, music, sound, production design, or costumes. With the notable exception of the producer, however, the range of the director's tasks is quite broad, and involves coordinating innumerable creative activities throughout the course of developing, shooting, completing, and marketing a film.
It shall be assumed here that the director is the individual who actively oversees the realization of a film from shooting script to finished product, harmoniously coordinating the creative activities of the key personnel involved in the production processes. He or she will liaise with each of these artists, deliberate over various expressive and/or technical options to be implemented, and arrive at a decision that is commensurate with the requirements of the developing work. Correspondingly, the director will also be answerable to the executive body that finances and/or distributes the work and therefore must ensure that production runs smoothly and within an allotted budget. The director's job, then, is twofold: to maintain a consistency of style and quality throughout production and ensure that the production itself proceeds efficiently and economically.
Serving as the funnel through which all of the decisions affecting a film's form and style are exercised, a director's primary task is to cultivate and coordinate the creative contributions of a production company's principal artists. In the interests of specificity and demystification, it is worth enumerating the various duties assigned to the director during all three stages of filmmaking: preproduction, production, and postproduction.
During the preproduction stage, the director's responsibilities can be divided into four principle tasks: (1) collaborating with the writer(s) on the development of the script; (2) assisting the casting director in hiring appropriate actors, and conducting rehearsals; (3) cooperating with the producer(s) in developing a practical shooting schedule; and (4) planning the overall visual "look" of the film with the production designers and the director of photography (DOP).
As in preproduction, there are four principal post-production areas in which a director's input is necessary: (1) editing, (2) visual effects, (3) music, and (4) sound. In most cases, an editor and director will develop the film's pace and rhythm, reinforce continuity between shots, trim moments of unwanted excess, and ensure that the montage generally serves to reinforce the work's intent. The visual effects category encompasses the manipulation of the raw footage by color timers, processing technicians, special effects designers, and an array of digital artists, compositors, and animators. Broadly speaking, a director will convey instructions to supervisors in each of these groups, indicating the specific "look" the director wishes to convey.