Offal is all the unused parts after butcher. Most "butchers" wouldn't consider organ meat offal since it is eaten by people, but I don't eat organ meat. I don't like feeding the intestines b/c of potential for parasite or disease (ecoli, salmonella, other feces born disease)
I also like to cook the bones in pressure cooker or crock pot depending on season (winter in the crockpot summer in the pressure cooker) until soft and grind them up in the blender and mix w/ cheap bread for added minerals.
Now I get it!
Great idea about bones. I have never heard anyone doing it.