The artful, graceful, powerful use of words. Nothing else comes close.
And, should you be uncertain, here is Emily Dickinson on the topic of words:
A word is dead When it is said, Some say. I say it just Begins to live That day.
Were I to never read any other poetry than that of Emily Dickinson, I would still receive full measure of what poetry is and can be. I remain awestruck whenever I read her.