What is mold? Mold (also called mildew) refer to fungi that may appear as a fuzzy-looking growth on the surface of organic materials in damp conditions, both outdoors and indoors. Unlike other fungi, the body structure of mold is made of fine thread-like structures. There are several types of mold. Some may appear grey, black, green, yellow, orange or various other colors. Though people will talk of grey mold, black mold, green mold, etc., these terms do not refer to a specific type of mold. Most molds have a velvety or wooly texture.