Poetry has many definitions. William Wordsworth defined poetry as "the spontaneous overflow of powerful feelings." Emily Dickinson said, "If I read a book and it makes my body so cold no fire ever can warm me, I know that is poetry." Dylan Thomas defined poetry as: "Poetry is what makes me laugh or cry or yawn, what makes my toenails twinkle, what makes me want to do this or that or nothing."
During the English Renaissance, dramatic poets such as John Milton, Christopher Marlowe, and of course, William Shakespeare gave us enough words to fill textbooks, lecture halls, and universities.
Poetry is artistically rendering words in such a way as to evoke intense emotion or an "ah-ha!" experience from the reader, being economical with language and often writing in a set form. Boiling it down like that doesn't quite satisfy all the nuances, the rich history, and the work that goes into selecting each word, phrase, metaphor, and punctuation mark to craft a written piece of poetry, but it's a start.