A graphics collection contains the visible elements of a page in an AFD. Layers of graphics are rendered in z-order. The lowest z-order layer is painted first, and the highest z-order layer is painted last. Consequently, the lower z-order layers are conceived of as "farther" from the human viewer of a screen (or printed page). And the higher z-order layers are "closer" to the human viewer. Objects that overlap will overdraw each other, whether rendering to screen or on a printer.  

The most important elements are the GfxImage element and the GfxDrawingArea element.

AFP Wrapper