ZBrush is a digital sculpting tool that combines 3D/2.5D modeling, texturing and painting. It uses a proprietary "pixol" technology which stores lighting, color, material, orientation, and depth information for the points making up all objects on the screen. The main difference between ZBrush and more traditional modeling packages is that it is more akin to traditional sculpting.Read more on Wikipedia
Have feedback on this skill? Let us know.