Moldy bread is bread that has developed a layer of mold, which is a type of fungus. This mold appears as green, blue, or white spots on the surface and can spread quickly. Mold thrives in warm, moist environments, making bread a common target. Consuming moldy bread can lead to health issues, as some molds produce toxins. To prevent bread from becoming moldy, it is best to store it in a cool, dry place or in the refrigerator. Using airtight containers can also help keep moisture out. Regularly checking for signs of mold can ensure that bread remains safe to eat.