lard or fatback
They hydrogenate the lard so it will have a long shelf life. You might find that some stores don't even bother to refrigerate it. If you render your own you can keep it in the freezer almost indefinitely. Recipes say you can keep it in the fridge for a couple weeks, but I recently found an unopened 2 month old pint container of lard that got pushed to the back of the shelf and it was just fine.
Fatback is what most folks make lard from. As for substitutes, it depends on what you're cooking. You can substitute bacon grease in some dishes (where you won't mind the salty, meaty taste it will add), but I wouldn't recommend that for baked goods. And if you have no shame, you can use Crisco. For baked goods or tamales, use butter.
Win Dixie, Albertson's, Winn Dixie all carry fatback and jowls in their meat cases. You can render any pig meat, from bacon to jowls to fatback, down into a clear liquid with some small chunks of meat floating in it, simply by a long, low temperature session on the stove top. good way to season a cast iron skillet as well.
When I was cooking chili competitively we tried to use leaf lard, which is the creme de la fat of lard. It comes from around the kidneys and is the purest.
Google "leaf lard" for several explainations of how to render it, or go to this site:
to purchase it, unrendered.
We get lard from the grocery store. It comes in white plastic tubs with green and red print on it, but for the life of me, I can't remember the brand name. It took me forever to find it because I assumed it would be near the meat department, but it was actually in the aisle with the oils. I've never bought fatback, so can't help you there :(.