Fungi are able to effectively digest food externally because, in all fungi but yeast, the organism consists of long, thread-like structures called hyphae which surround and grow into the food source, living or dead. These hyphae can grow extremely rapidly. In 24 hours, 0.6 miles of hyphae can be produced. Fungi generally have two stages, the feeding stage and the fruiting body. The feeding stage consists of hyphae that are involved in digestion of food.
Some fungi eat dead organisms.
These fungi are often beneficial since they contribute to the decomposition of dead organism and the recycling of organic molecules contained in them. These fungi are called decomposers. Other fungi utilize living organisms as a food source. These fungi are parasites. Some of these parasites are disease causing organisms or pathogens.