You can use one of your objects as a cookie-cutter and punch out material from another object.  If the star is placed in the center of the circle and "Punch" is selected from the "Combine" menu you end up with an object that looks like this.

(Figure 10.6)

The object that you want to use as a punch must be at the top of the stacking order. In this case the star was sitting on top of the circle when the punch was applied to the combination. If the star were on the bottom of the stack when you applied the punch you would end up with no content in your document window because the circle is larger than it.  Be conscious of the stacking order of your objects when you create combinations. If the resulting object of a combination isn’t quite what you expected it to be it might be because your stacking order isn’t quite right.