Is it the critics who decide art is art, or do people themselves decide what is art?

One person's art is not another person's art, so why are some people qualified to label something as art? Anybody can have an opinion, you don't have to have a degree to have an opinion and to me, what you think is art is your opinion. To me, art is a talent, like a sculpture or a painting, none of this "modern art" like Damien Hirst's half a cow, there again that is only my opinion. Thoughts anyone?