Some would say that art is expression. It's a way of sharing how we see the world, an extension of self expression.
Others would say that art is something with a communicative or educative purpose, something that expresses an idea, emotion or even world view.
I believe art is what makes us uniquely human. Art doesn't necessarily serve a purpose essential to our survival. Whether it's visual or auditory or another art form, we don't need it to keep our biological selves alive.
We are the only species that has conceived of the idea of making beautiful things for the sake of simply appreciating beauty.
Art is important to us because it gives us a window into our souls. It is an entry point to understanding what it means to be human.
Seth Godin said it so well. "Art is what we call... the thing an artist does. It's not the medium or the oil or the price or whether it hangs on a wall or you eat it. What matters, what makes it art, is that the person who made it overcame the resistance, ignored the voice of doubt and made something worth making. Something risky. Art is not in the ...eye of the beholder. It's in the soul of the artist."