Polymer clay is a plastic clay, made of polymers. Polymer clay is sold under the brand names Fimo, Cernit, Sculpey, and Premo. That's just in the United States. Fimo and Cernit are imported from and sold outside of the US, and there are other brands that are sold in other countries.
Polymer clay can be baked in your home oven, it doesn't require a kiln like traditional clay. Additionally, it stays soft and malleable until it is baked, unlike traditional clay. These clays are usually available in a wide assortment of colors, which allows them to be used in a variety of unusual techniques.
One of the most popular techniques to use with polymer clay is known as canework, also called millefiori after the Italian glass working method. This technique involves layering and stacking different colors of the clay in a loaf, which results in a pattern or image that is consistent throughout the loaf. Slices can then be taken from the ends of the cane, or loaf, that can be applied to objects such as beads or household ornaments or whatever one likes. The cane can be compressed and stretched to reduce the image to whatever size one likes.