What Is Poetry‪?‬

Has poetry lost its story-telling power and persuasion? What is the difference between poetry and prose? Is the difference between a good, bad or ugly poem merely a subjective preference? Are there any objective criteria for deciding whether a poem is good, bad or ugly? How would you define good, bad and ugly? How would you explain what poetry is to someone who doesn't read or write poetry? How would you explain what a tree is to a Martian?