Indicates a window's position in a stack of overlapping windows. This window stack is oriented along an imaginary axis, the z-axis, extending outward from the screen. The window at the top of the Z order overlaps all other windows. The window at the bottom of the Z order is overlapped by all other windows. An application sets a window's position in the Z order by placing it behind a given window or at the top or bottom of the stack.
Enlarging a selected window or portion of a graphical image in order to see finer details in the image.