Found in the lower stomach of fowl, this muscular pouch grinds the bird's food, often with the aid of stones or grit swallowed for this purpose. The portion that actually does the work is in the center of the pouch and is usually removed before the gizzard reaches the market. Gizzards can be very tough unless cooked slowly with moist heat, such as braising.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.