What is the difference between Cajun and Creole cuisine?
The previously accepted answer contains a good link, but not any information here on Seasoned Advice, so I thought I would write out a few things from my understanding after having developed an abiding interest in Cajun foods over the past decade.

Basically, Creole is a much broader term with a longer history. While it is perhaps inaccurate to say Cajun is a 'subset' area and culinary style, it is more geographically- and flavor-specific than just saying Creole. The history of people and region identified as Creole (on the American continents) goes back a long ways, and Cajun is a more recent phenomenon. Creole can also refer to other peoples and regions other than just in the South/Central parts of North America, though such use in the United States is a distant memory.

In the past century, the "Cajun" term has certainly attained an independent status as a self-identified people, region, and flavor -- the last no doubt owing to the flavor potency of their offerings. Which offerings, in my opinion, when consumed, are nearly always exquisitely enjoyable examples of perfection in the experience of food.