The bluish smoke that can then be seen means the oil is close to burning and is the temperature at which fats and oils begin to break down.
Nutrition and flavor degradation occur at these temperatures. The chemical composition of the oil changes, sometimes with effects that are harmful to health.
A low smoke point means the oil should not be cooked with at all, or only slightly.
A high smoke point oil should be used for cooking at higher temperatures, for example pan frying.
Here is the smoke point of a few of the more common refined cooking oils,
Canola 400 degrees
Cottonseed 420 degrees
Sunflower 440 degrees
Corn 450 degrees
Peanut 450 degrees
Olive pomace 460 degrees
Soy 460 degrees
Extra-light olive 468 degrees
Safflower 510 degrees