Cloning is the process of copying a picture of a animal in real life and pasteing it on a models skin. It is done with the Clone Stamp Tool, available in many programs such as Gimp and Photoshop. In order for one to clone in Gimp, the area of which the brush will copy from is defined by holding Ctrl and selecting the area or part of the picture. From there you shift to your skin, which you simply paint onto. The same is with photoshop, however there are differences between the too. For example, one must hit Alt instead of Ctrl in photoshop. The defined area controls are also differn't. However, like painting, they both can have there opacity changed.