La trahison des images, or "The Treachery of Images," is a famous painting from a series by Surrealist René Magritte, which features a painting of a pipe over the words "Ceci n'est pas une pipe," meaning "This is not a pipe." The point is that it is not a pipe; it is a painting of a pipe.

http://en.wikipedia.org/wiki/The_Treachery_of_Images
la trahison des images