Andouille sausage is a hallmark in Cajun dishes such as gumbo and jambalaya, most likely brought to Louisiana by the French or Germans. Traditionally, Cajun andouille sausage is made with ground pork butt or shank, pork fat, garlic, thyme, red pepper, cayenne, salt and black pepper. The mixture is then stuffed into either a beef or pork casing, and then it is smoked over pecan wood and sugar cane. It is deeply spicy and smoky, with degrees that vary by region, recipe and cook.
There are also milder French and German versions of andouille, but these are very different sausages and they can't be used interchangeably in a recipe (if the recipe simply calls for andouille, it's usually safe to assume it's the Cajum version).