An Italian omelet that usually has the ingredients mixed with the eggs rather than being folded inside, as with a French omelet. It can be flipped or the top can be finished under a broiling unit. An omelet is cooked quickly over moderately high heat and, after folding, has a flat-sided half-oval shape. A frittata is firmer because it's cooked very slowly over low heat, and round because it isn't folded.