Sculpey III is a brand of polymer clay.
It is a good clay for beginners and kids due to its softness, although it is too soft for some techniques (such as Millefiori, for example). Sculpey III is the most popular brand of Sculpey clays. Other types of Sculpey include Sculpey Original, Sculpey Soft, and Super Sculpey.
Please refer to my tutorial about different brands of polymer clay.