Kosher salt is salt used for the koshering process, the preparation of meats according to Jewish dietary laws. It comes in coarse particles, often flakes, and is sprinkled on the freshly butchered meat for the purpose of drawing out blood. Because it’s meant to remove impurities, the salt itself is not iodized. Many cooks like to use kosher salt in general cooking for its relative purity and ease of dispensing by hand.
From the book On Food and Cooking (2nd edition) by Harold McGee. © 2004 Harold McGee. By permission of Scribner, a division of Simon & Schuster, Inc.