This is a little excerpt from his biography that I thought really captured what he was about!
"Andrei Tarkovsky was the most spiritual and poetic director of all time. For him cinematography was not entertainment, it was art in the best meaning of this word. He was one of the most educated directors – he studied music and painting, he was born into the family of a poet. Being a versatile artist he was able to create a synthesis of arts in his films. Film for him was not just a reflection of reality; it was more like a poem or a dream.
Ingmar BergmanWhen film is not a document, it is a dream. That is why Tarkovsky is the greatest of them all. He moves with such naturalness in the room of dreams. He doesn't explain. What should be explained anyhow? He is a spectator, capable of staging his visions in the most unwieldy but, in a way, the most willing of media.
For him films were much more than a synthesis of arts. As he wrote himself, he wanted to sculpt time and to reach into the inner truth of our existence.
"For me film - is a way to reach the truth and I am trying to do it to the fullest extent of what I am capable of. I am profoundly convinced that the process of creating a film does not end after it was finally made ready for the movie theatre. The act of creation takes place in the auditorium at the time of watching the film. Therefore, the viewer for me is neither my consumer, or a judge, but a co-creator, co-author.""