So you can get two different messages about a square from this figure. One message has the square in front, with glowing lines; the second message has the square in back, with lines that don’t glow. Notice that all four lines glow, or else all four lines do not glow. You never see, say, two lines glowing and two not glowing. Why? Because your visual system has united all four lines into a single unified message: a square. It has “entangled” the four lines into a single object so that what happens to one line must happen to all.
