Poetry is a literary work which is meant to be read aloud or spoken. It relies strongly on word choice, sounds, and imagery to create a mood in the audience's mind or ear which may be romantic, ominous, wistful, sensual, inspiring, or daring.
Poetry may be defined in opposition to prose, which is language which is meant to convey meaning, with lesser emphasis on mood, word choice, and exact form of expression. While prose can be produced spontaneously, poetry must usually be composed with care over time.
Poetry in the classroom
Poetry in the classroom may be an emotive subject, as some teachers quite like using it while others detest it. It's usage therefore probably depends more on the teacher's pre-conceived ideas about poetry than on its utility in language teaching.
Joy L. M. Brown, Rhymes, Stories and Songs in the ESL Classroom, The Internet TESL Journal, Vol. XII, No. 4, April 2006