Sausage is almost like barbecue. Each region (and sometimes, country) has its own kind that uses ingredients and seasonings common to that specific area.
It’s sort of like mustard base, vinegar base, ketchup base and white base barbecue sauces. Sausage is what it is, depending on where you live.
In the South, sausage is usually a mixture of ground pork, pork fat, sage and peppers and other spices that’s made into patties and fried.