What is Art?

What exactly is art? Different people define it in different ways, and to me art is anything that combines creativity and displays emotion. When I look at a piece of art, I expect it to convey some sort of message by the artist, that explains his thoughts for doing this piece. There are several pieces of arts that I admire that come in all forms. Whether it's a Monet painting, an ancient greek sculpture, an Edgar Allen Poe poem, or even a Rolling Stones song, I see it all as art because whoever created it wanted the viewer to get something from it.
Although created millions of years ago, cave paintings from the stone age truly amaze me. Its crazy to think that art existed in a time before languages, and any form of education, and how a message was still developed through the painting. Dating back to prehistoric times, these paintings were a way for people to communicate. But what really strikes my curiosity, is the fact that a caveman had this idea, discovered how to put these messages "on paper" and passed it on to someone else. This form of art still remains a big mystery and has many unanswered questions, but the way I see it, its the first type of art far before the concept of art even existed.