Film essays (or “cinematic essays”) consist of the evolution of a theme or an idea rather than a plot per se; or the film literally being a cinematic accompaniment to a narrator reading an essay. From another perspective, an essay film could be defined as a documentary film visual basis combined with a form of commentary that contains elements of self-portrait (rather than autobiography), where the signature (rather than the life-story) of the filmmaker is apparent. The cinematic essay often blends documentary, fiction, and experimental film making using a tones and editing styles.
17] The genre is not well-defined but might include works of early Soviet parliamentarians like Dziga Vertov, present-day filmmakers like Chris Marker, Agnes Varda, Michael Moore (Roger and Me, Bowling for Columbine and Fahrenheit 9/11), Errol Morris (The Thin Blue Line), or Morgan Spurlock (Supersize Me: A Film of Epic Proportions). Jean-Luc Godard describes his recent work as “film-essays”.  Two filmmakers whose work was the antecedent to the cinematic essay include George Melies and Bertolt Brecht.Georges Melies did a film about the coronation of Edward VII in 1902 which mixes actual footage with shots of a recreation of the event.
Bertolt Brecht was a playwright who experimented with film and incorporated film projections into some of his plays.  David Winks Gray’s article “The essay film in action” states that the “essay film became an identifiable form of film making in the 1950s and ’60s”. He states that since that time, essay films have tended to be “on the margins” of the film making world.
Essay films have a “peculiar searching, questioning tone” which is “between documentary and fiction” but without “fitting comfortably” into either genre. Gray notes that just like written essays, essay films “tend to marry the personal voice of a guiding narrator (often the director) with a wide swath of other voices”.  The University of Wisconsin Cinematheque website echoes some of Gray’s comments; it calls film essays an “intimate and allusive” genre that “catches filmmakers in a pensive mood, ruminating on the margins between fiction and documentary” in a manner that is “refreshingly inventive, playful, and idiosyncratic”.