Persona
This is my definition of art made into a movie, You might want to find the "true" meaning of persona and that's still fine, but seeing that this movie means something different to every person who watches it, is what makes this movie so important in the history of cinema.
For me, a masterpiece about loneliness and how we behave in society, hiding our true self just to be likeable. You don't need to understand art, You are more than great just by appreciating it.