Dear Nicole Nicole,
From my experience, your question does not really compute...so please look over my answer to discern what your instructor is really trying to ask...
...because ALL abstract art is representational; that is, no matter how illusory, still based on a recognizable reality you will find here in the world of time and space - even a Picasso with three eyes and your arm coming out of your head.
The breakthrough from abstract into non-representational art was in the 1950's, and two masters were Jackson Pollock and Mark Rothko; pure ideation, rhythm, meditation.
So Van Gogh STARRY NIGHT still represents a night sky, but Post-Impressionism he is beginning to abstract; introducing metaphorical, mythical dimensions a camera does not capture - for example the sky-spiral formations found throughout nature in everything from a seashell to an opening bud to a galaxy.
Here is a Jackson Pollock, also a Rothko; these are considered truly non-representational.