Mildew is a type of fungus that typically appears as a thin, powdery coating on surfaces. It thrives in warm, damp environments and is commonly found in places like bathrooms, kitchens, and basements. Mildew can grow on various materials, including wood, fabric, and paper, and it often has a musty odor. While mildew is not as harmful as some other fungi, it can still cause damage to materials and may trigger allergic reactions in sensitive individuals. Regular cleaning and proper ventilation can help prevent mildew growth, making it important to maintain a dry environment in your home.