Imagery is all of the pictures and sensations a piece of writing conjures up in your noggin. Imagery is the key to literature—especially poetry. If you're reading a description that engages any one of your five senses, you're reading imagery, folks.
Shmoop loves imagery so much we that dedicate entire sections of our learning guides to it. Check out our discussions of imagery in J.D. Salinger's Franny and Zooey and Emily Dickinson's poem "I heard a Fly buzz – when I died –".