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, paper, and fabric, and it often has a musty odor. While mildew is not as harmful as some other fungi, it can still cause health issues, especially for individuals with allergies or respiratory problems. It can also damage materials over time if left untreated. Regular cleaning and proper ventilation can help prevent mildew growth in homes.