Sausage is ground meat that is salted and seasoned for preservation. It comes in many varieties worldwide defined by their meat, seasoning, casing, and preparation method. Common casings include natural intestines, collagen from cattle hide, and fibrous cellulose. The meat filling consists of ground pork and fat with optional variety meats and binders. Non-meat ingredients like salt, curing agents, spices, and extenders are added to flavor and preserve the sausage. Famous varieties include salami, chorizo, bratwurst, andouille, and hot dogs.