A documentary film is a nonfictional motion picture intended to document some aspect of reality, primarily for the purposes of instruction or maintaining a historical record. Such films were originally shot on film stock—the only medium available—but now include video and digital productions that can be either direct-to-video, made into a TV show or released for screening in cinemas. "Documentary" has been described as a "filmmaking practice, a cinematic tradition, and mode of audience reception" that is continually evolving and is without clear boundaries.
In popular myth, the word documentary was coined by Scottish documentarian John Grierson in his review of Robert Flaherty's film Moana (1926), published in the New York Sun on 8 February 1926, written by "The Moviegoer" (a pen name for Grierson).
Grierson's principles of documentary were that cinema's potential for observing life could be exploited in a new art form; that the "original" actor and "original" scene are better guides than their fiction counterparts to interpreting the modern world; and that materials "thus taken from the raw" can be more real than the acted article. In this regard, Grierson's definition of documentary as "creative treatment of actuality" has gained some acceptance, with this position at variance with Soviet film-maker Dziga Vertov's provocation to present "life as it is" (that is, life filmed surreptitiously) and "life caught unawares" (life provoked or surprised by the camera).