A mold or mould is one of the structures that certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi. Not all fungi form molds. Some fungi form mushrooms; others grow as single cells and are called microfungi.
Penicillium mold growing on a clementine
Spinellus fusiger growing on the mushroom Mycena haematopus
Several species of mold growing on a slice of bread.
Mold on dried Hibiscus sabdariffa
A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the traditional eukaryotic kingdoms, along with Animalia, Plantae and either Protista or Protozoa and Chromista.
Fungus
Omphalotus nidiformis, a bioluminescent mushroom
Bracket fungi on a tree stump
Widespread white fungus in wood chip mulch in an Oklahoma garden