Drop shadow
A dark overlay that covers a section of text or a graphic that makes the object appear three-dimensional. In operating systems and software programs, drop shadows are commonly used to bring attention to an object, such as a dialog box when it opens on the screen. In the below image, you can see the drop shadow effect on "Computer Hope".
In the above example, we're creating a drop shadow on the "Computer Hope" layer effect in Adobe Photoshop. As can be seen in the Effects dialog box, we have several different ways to adjust the appearance of the drop shadow. For example, the opacity, angle of the shadow, distance of the shadow, and how blurry the shadow appears.
Also see: Operating system definitions, Shadow