Definition: Jambalaya is a Creole or Cajun rice dish usually made with chicken, sausage, shrimp and/or crawfish simmered in flavorful stock along with rice, tomatoes, and seasonings.
Proper jambalaya is thicker than a soup, although jambalaya soups have certainly been served. Nor is it altogether a stew, although jambalaya does share certain characteristics of stew, including the fact that it is simmered slowly in stock or some other liquid.
The closest corollary to jambalaya is the Spanish dish Paella, which again is neither a soup nor a stew but is likewise probably best described as a rice dish. Indeed, jambalaya is one of the clearest examples of the influence of Spanish cuisine in the New World.
There are a number of jambalaya variations, with the main distinction being between Creole jambalaya, which is made with tomatoes, and the Cajun version, which isn't. Apart from that, the ingredients generally include onions, celery, and red or green peppers, and the meats can be anything from chicken and ham to turkey, duck or even alligator.
The sausage in jambalaya can be either fresh or smoked. Andouille, a spicy smoked pork sausage, is a common jambalaya ingredient, as is chaurice, which is a spicy fresh sausage.
Possibly the one ingredient you'd pretty much have to have in any jambalaya is rice.
Here's a great Jambalaya Recipe.