Often confused with salt pork (which comes from the sides and belly of a pig), fatback is the fresh (unsmoked and unsalted) layer of fat that runs along the animal's back. It is used to make lard and cracklings and for cooking -- especially in many Southern recipes. Salt-cured fatback is also sometimes available. All fatback should be refrigerated: fresh up to a week, cured up to a month.
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.