Draw two overlapping shapes, a circle and a square, each a different color. Now create an exact copy of those two shapes, only in the copied version, group the two objects together by selecting them and choosing Object > Group. So now you’re looking at two design elements, each identical in appearance, only one is made up of two separate objects, and one is made of two objects that are grouped together . Select the first set of objects and choose Effect > Stylize > Drop Shadow and apply the default settings. Now select the grouped objects and apply the same drop shadow.

The design elements shown here are identical except for one fact: the element on the right has been grouped.

The first design element appears to have drop shadows applied to each object individually. The second design element—the group—has a single drop shadow applied to it, as if the two separate shapes were really one shape. This difference in appearance occurred because in the second design element, Illustrator applied the drop shadow not to the actual objects themselves, but to the container that has the two objects inside of it—the group. Now, select the group and choose Object > Ungroup, and the drop shadow disappears! By removing the container (ungrouping), you’ve removed the effect that was applied to that container.