Essays / How to write a essay on "what is art"? [4]

Hi, I have to write an essay for my "art class", but the problem is that I need a little help on it. The theme has to be: What is art. Based on this, i think I will have to do an expository essay, but i dont know what to write in it (since it has to be three pages long). i was thinking of putting the definition of art, some types of art, my personal opinion on what is art, famous pieces and artists.

How do you think i should write it? Should i write all of the ideas i told you, or would it be better to just focus on "what is art"?