Mold is alive, but it is neither a plant nor an animal. Mold is a type of fungus. It is part of a group of living organisms that are very common and serve an important role in the environment. Penicillin, an antibiotic that has saved many lives, is a type of mold, as is yeast.
However, mold can grow on bread and other types of food, making it unfit to eat. Mold can grow on the walls, floors and ceilings of your home as well as on your personal possessions. People often refer to some household molds as mildew, although the term also can apply to molds found outdoors.