meaning of art

As in, "Hey, what's with that piece of conceptual art. I don't get it. Like, I could do that."
Love it or hate it, many people have strong opinions on modern art. Many don't even agree on the definition: it ranges from a physical object or painting, to an idea or dance. These days, it seems like you can put a blank canvas on the wall and call it "art."
Art has always tended to speak truth to power, to enlighten us, to challenge us, to stretch our understanding of ourselves and our place in the universe. It wasn't always so self-referential, so blasé, so up for grabs.