A documentary film is a non-fictional, motion picture intended to "document reality, primarily for the purposes of instruction, education, or maintaining a historical record". 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". Documentary films were originally called actuality films, and were one minute, or less, in length. Over time, documentaries have evolved to be longer in length, and to include more categories; some examples being: educational, observational, and docufiction. Documentaries are meant to be informative works, and are often used within schools, as a resource to teach various principles. Social media platforms, such as YouTube, have provided an avenue for the growth of the documentary film genre; These platforms have increased the distribution area and ease-of-accessibility; thereby, enhancing the ability to educate a larger volume of viewers, and broadening the reach of persons who receive that information.