An image is a vivid description that appeals to the senses. Images are most often found in poetry, although writers can also use images to make their prose more striking or memorable. (See also figures of speech.)
For example, in "The Angry Winter," Loren Eiseley brings to life scientific information about the ice age by including sensory images of winter, such as this cold and silent scene.
As I snapped off the light the white glow from the window seemed to augment itself and shine with a deep, glacial blue. As far as I could see, nothing moved in the long aisles of my neighbor's woods. There was no visible track, and certainly no sound from the living. The snow continued to fall steadily but the wind, and the shadows it had brought, had vanished.