Art, as a general term, is a piece that is in a continuous state of flux which can be expressed visually, auditor-ally, vocally, and/or physically using a variety of mediums be it canvas and paint, musical notation and instruments, bodily movement, the written word, or fabric and colour.
“Good” art tends to move the soul, whether it is due to pure aesthetic beauty, melodic harmony, physical skill or the ability to force the viewer to question and reconsider what he/she has seen as “the truth” until that given moment. It may be an assault to the senses, may evoke emotion or scream out at social political injustice (my favourite!).
It also changes with time and space, engaging in conversation with each and every viewer. Whether one realizes it or not, viewing art always involves a conversation with the piece itself. This conversation becomes attached to the piece. And so, the given piece is in a constant state of flux. When the conversation dies, the piece lives on in the space and time where it was an active part of its environment till it may or may not resurface at another point in time.