What is "sunny-side up"?

Sunny-side up eggs are fried eggs where the yolks remain runny and are cooked on only one side, facing up when served. The eggs are fried in a pan or skillet until the whites are set, but the yolks remain soft and runny. Unlike over easy eggs, sunny-side up eggs are not flipped during cooking. The soft yolks remain exposed on top, "facing up" when the eggs are served. The name "sunny-side up" refers to the yolks facing up like the sun.