Documentary films constitute a broad category of nonfictional motion pictures intended to document some aspect of reality, primarily for the purposes of instruction or maintaining a historical record. A "documentary film" was originally a movie shot on film stock—the only medium available—but now includes video and digital productions that can be either direct-to-video or made for a television program. "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.