A hypha is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium.
Hyphae of Penicillium
Hyphae growing on tomato sauce
Aspergillus niger
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