Figure and Ground

In figure and ground perception, our minds seek to separate a distinct object from its surroundings and background. The image that you perceive is called the figure while everything else becomes the ground. Often, this relationship reverses as we perceive different objects within the same image. In the picture below, we see a popular optical illusion that illustrates the figure-ground relationship. When you look at the image, do you see a vase? Or maybe two faces looking at one another? If you see the vase, then this would be the figure while the white area becomes the ground. Inversely, if you see the two white faces, then they are the figure while the golden vase becomes the ground. Your perception of these two objects will continuously alternate back and forth.

Image from http://makingartfun.com/htm/f-maf-art-library/face-vase-drawing-lesson.htm