What is the difference between 3D desktop themes and regular themes?

The difference between a 3D desktop theme and a regular desktop theme is that the 3D desktop theme features 3D shapes and images. Any component of the theme may feature 3D images.

A desktop theme is a graphical user interface, abbreviated GUI, that is customized to replace the computer's default sounds, icons, pointers, wallpapers or screensavers. These are often chosen to reflect the personal interests and tastes of users. Although most desktop themes are chosen for home use, they may not be allowed in professional environments because some themes are only found through an unknown source, posing a possible security risk to the computer.