Shadows create an appearance of depth. An element's shadow appears on any element behind it. You can create a variety of shadow effects, or remove the shadow from an element.
The further the shadow is from the element the higher the element appears.
A high blur value makes the element's shadow appear more diffuse; a low value gives the shadow a more sharply defined edge which more common in comic lettering.
Note: Don't use the Opacity slider at the bottom of the Graphic inspector, which changes the opacity of the entire element (not the element's shadow).