The Eyeballs: What They See Is What You Get
The eyeballs in the Layers palette determine which layers will be visible in your document as well as which ones will print. The eyeballs turn on and off in a toggle effect when you click them: Now you see them, now you don't.
If you turn off all the eyeballs in the Layers palette, Photoshop will fill your screen with a checkerboard. This checkerboard indicates that there's nothing visible in the document. (If Photoshop filled your screen with white instead, you might assume that there was a layer visible that was filled with white.) You can think of the checkerboard as the areas of the document that are empty. When you view a single layer, the checkerboard indicates the empty areas of that layer. As you turn on the other layers in the document, the checkerboard is replaced with the information contained on those layers. When multiple layers are visible, the checkerboard indicates where the underlying image will not be obstructed by the elements on the visible layers (Figures 3.11 to 3.14).
Figure 3.11. The checkerboard indicates a transparent area.
Figure 3.12. The Layers palette view.
Figure 3.13. As more layers become visible, the transparent areas become smaller.
Figure 3.14. The Layers palette view.
