Gumbo is a specialty Creole stew made from shellfish, meats, okra, tomatoes, onions, sausage, ham and a variety of other shellfish. Two key ingredients include a rich roux that thickens and flavors the broth, and file powder [FEE-lay] powder. Some gumbo recipes are historically thickened only with okra rather than file. Although "instant roux" powder can be substituted it is not preferred. You can read more about the history of gumbo, here.
Gumbo is typically served over rice.