Precious Metal Clay is not the same thing as polymer clay, but they are often used together in jewelry and works of art. PMC is essentially microscopic particles of silver or gold suspended in an organic binder.
PMC starts out as a malleable material similar in consistency to polymer clay. It can be worked with in the same way as polymer clay. (The ease of workability is perhaps PMC's greatest attribute.) However, once PMC is cured (or "fired")-at a higher temperatre than polymer clay-the binder burns away. What is left is a solid metal-in whatever shape or form it was sculpted to prior to firing-- that can be worked with like any other metal.
There are different types of PMC with different qualities and characteristics. PMC costs considerably more than polymer clay, and though one may use some of the same tools and techniques with both, there are significant differences between the two materials and how they are cured/fired. You'll want to read more about PMC before deciding if this medium is for you.