Who decides what art is and why?

The Artist his/herself decides what art is! There is a story behind every art piece. Stories from the artist because the artist can make the decision of the purpose of the piece of art. Art isn't always drawing, it could be painting or building or even just music! Artists usually put their all and feeling and time into it. And usually they're trying to get a statement out using art! So the Artist itself gets to decide what art is.

The artist decides, because whatever they want can be art