A cranking rod is a type of casting rod, only a more specialized one. Cranking rods are designed exclusively for crankbait lures, which themselves are usually pulled along the bottom of a lake or river bed by a boat. Their actions are a bit slower, which can lead to a more forgiving pull with less snagging.
For the most part, anglers consider casting rods to be more versatile, though there are plenty of folks who use casting rods for crankbait fishing once they know what they’re doing. All it requires is to reduce the drag a bit so you don’t encounter any sudden snapping due to fast action.