Outside of Louisiana, the flavors meld and the line between the two cuisines blurs. But there is a difference. Defining that difference can be tricky. It helps to know the distinctions between the two cultures.
Creole culture, much like its cuisine, is a melting pot of African, French, Spanish and Italian influences. Immigrants from all of these countries settled in Louisiana after the Louisiana Purchase and contributed bits and pieces of their culture and cuisine. From Africa, creole cuisine gains spices; from the French aristocrats it incorporated butter and heavy cream. The Spanish contributed hot peppers, while the Italians added tomatoes and cheeses. The first Creole cookbook in English was La Cuisine Creole: A Collection of Culinary Recipes, published in 1855.
The original Cajuns were decedents of the Acadians, who were exiled from present-day Nova Scotia circa 1755. Many refugees settled in French-Colonial Louisiana and were forced to live off the land. They became farmers and hunters. The cuisine reflects this way of life in its inexpensive, readily available ingredients and how they are used. You'll see many common local ingredients such as corn, rice, beans, and lots of pork. Pork fat was used as a substitution for the butter they were accustomed to. Modern Cajun cooking methods are adaptations of recipes passed down through African generations in the American South. They are one of the distinctive qualities of Cajun cooks. And if it weren't for them, the world would be worse off without Etouffee (pictured) or Fricassee.
CREOLE = French, Spanish, Italian, and African Cuisines. That means lots of butter, tomatoes, and higher-end ingredients.
CAJUN = French and Southern cuisines. This includes pork fat, lots of spices, and cheap, readily available ingredients.
Creole, Cajun... two different things.