Poetry has a “form,” a shape, or a division into parts. 

Poetry has an effect on the reader.

Poetry creates images (pictures in our mind).

Poetry uses figures of speech; it plays with the images that work in your mind .  For example, the sentence, “Jane is as pretty as a rose,” is called a simile.  And “Jane is a rose” is a metaphor. Similes and metaphors are poetic techniques. Poets use those techniques to create pictures in your mind.