There are two types of imagery used in works of fiction: literal imagery and figurative imagery. Both types rely on the sensory experience of sight.
Literal imagery is the description of the visible world: people, places, objects, events, etc.
Two doors from the corner, on the left hand side going east, the line of buildings was broken by the entry of a court; and just at that point, a certain sinister block of buildings thrust forward its gable on the street. It was two stories high; showed no window, nothing but a door on the lower story and a discolored wall on the upper; and bore the marks of prolonged and sordid negligence. The door, which was equipped with neither bell nor knocker, was blistered and distained. Tramps slouched into the recess and struck matches on the panels; children kept shop upon the steps; the schoolboy had tried his knife on the moldings; and for close on a generation, no one had appeared to drive away these random visitors or to repair their ravages.
Figurative imagery will use physical descriptions of real things to express an abstract idea that is hard to put into words. This type of imagery usually appears as metaphors, similes, personification, or metonymy (using a characteristic detail in place of a name).
Let’s look at an example!
The street was small and what is called quiet, but it drove a thriving trade on the weekdays. The shop fronts stood along that thoroughfare with an air of invitation, like rows of smiling saleswomen. Even on Sunday, the street shone out in contrast to its dingy neighborhood, like a fire in a forest; and with its freshly painted shutters, well-polished brasses, and general cleanliness and gaiety of note, instantly caught and pleased the eye of the passenger.
More often than not, writers will combine literal and figurative imagery in the very same description:
The fog still slept on the wing1 above the drowned city, where the lamps glimmered like carbuncles2; and through the muffle and smother of these fallen clouds4, the procession1 of the town’s life was still rolling in through the great arteries3 with a sound as of a mighty wind. But the room was gay with firelight4. In the bottle the acids were long ago resolved4; the imperial dye had softened with time4, as the color grows richer in stained glass windows2; and the glow of hot autumn afternoons on hillside vineyards4, was ready to be set free1 and to disperse the fogs of London.4
Each type of imagery is labeled with a superscript number:
The purpose of Imagery is to:
Source: Examples taken from Robert Louis Stevenson's The Strange Case of Dr. Jekyll and Mr. Hyde