It's a kind of gelatinous headcheese that also contains pig's feet and other porcine parts, always sliced thick and served cold.
British Dictionary definitions for headcheese
headcheese
/ˈhɛdˌtʃiːz/
noun
1.
(US & Canadian) a seasoned jellied loaf made from the head and sometimes the feet of a pig or calf Also called (in Britain and certain other countries) brawn