Gumbo is a soupy, stewy dish that’s a mainstay of Creole and Cajun cuisine. “Gumbo” is an African word for okra, and most gumbos use it for flavor and as a thickener for the stock. File powder (powdered sassafras leaves) is used to thicken too. You can use one or the other, and some use both. Building a gumbo often begins with a roux (butter or other fat cooked slowly with flour, until brown). The roux adds color and a delicious toasty flavor.
Traditionally, the ingredients were what one had on hand. Seafood, chicken, and meat are all used alone or in various combinations. There are infinite ways to make gumbo.