A 'core' is the section of the chip where the fundamental logic of the design is placed. A die, which consists of core, is small semiconductor material specimen on which the fundamental circuit is fabricated. IC's are fabricated on a single 9 inch or 12 inch diameter silicon wafer, which contains hundreds of mirror images of the fundamental logic. This wafer is then cut into small pieces, each piece has similar functionality of the fundamental logic. This is called 'die'