Usually the term "soul food" refers to Black cuisine
, though in the South
it has come to be synonymous
with all Southern-style cuisine.
Most dishes considered soul food are descended from slave cooking. You can see this in their use of inexpensive foods (often parts that other cuisines might consider leftover) and African cooking styles (stewing, frying) and spices.
Soul food does include popular dishes like fried chicken, ribs, coleslaw, etc but the more traditional and less mainstream dishes tend to follow these patterns:
Meats tend to be the "less desireable" parts of the animal (pig's knuckles, pig's ears, tripe, hog maws), animals which could be hunted for food (deer/venison, squirrel, opossum), or native fish (catfish, trout, shrimp, crawdads)
Vegetables tend to be the "leftover" parts: the greens of turnips, collard and mustard greens, the hominy of the corn (whence grits). Beans are very cheap and very popular. There is also a dominance of African vegetables like yams, okra, and peanuts.
Many dishes are cooked in a single pot, and are heavy on the chile.
Other notes on soul food:
This term is being used more and more to mean whatever food you grew up with. I actually kind of like that. I like the term soul food. Soul food should be comforting, warming, and nurturing. It should be what your mom made for Sunday dinner when you were a kid.