What is Art?

I think everything is art. I have thought this every since we had a school play and one of the songs was about how everything was art. It did not seem to have much of an effect on me at the time but I have thought of it a lot since then.
People have asked me if I thought things like trees and stuff were art even if no one made it, yeah I think it is. Like a snowflake, when someone takes a picture of a snowflake it becomes art, but I think it was art even before it was picture. If someone took a picture of some old lady smoking a cigar or something and put it in a museum people might go crazy about it, but would they go crazy if they had seen that old woman on the streets? Not unless they had a camera. So where is the line drawn? What is the difference between when this old lady is a photo and when she is an actually three dimensional thing? The only reason I can think of is that someone had the intent of making it art. And maybe that's the answer, if there is an intent, it's art, no matter what else happens.