"Rotten eggs" refer to eggs that have gone bad due to bacterial growth or spoilage. When eggs spoil, they can emit a strong, unpleasant odor, often described as similar to sulfur or rotten cabbage. This smell is caused by the breakdown of proteins and the release of gases, particularly hydrogen sulfide. To determine if an egg is rotten, a simple test can be performed by placing it in water. Fresh eggs will sink and lie flat on the bottom, while rotten eggs will float due to the buildup of gases inside the shell. Proper storage in the refrigerator can help extend the freshness of eggs.