Microbe World indicates that fungi absorb food from their immediate surroundings directly through their cell walls unlike animals, which eat food, and plants, which produce their own food through the process of photosynthesis. Kew Gardens adds that fungi function like an inside-out version of an animal's stomach. Instead of eating food and digesting it internally, fungi first dissolve food into simpler nutrients and then absorb the food after they digest it.
Microbe World states that most fungi are "grazers," passively eating the food that they grow on. Other fungi, however, are "hunters," trapping active prey that pass their way. For example, these fungi may utilize sticky substances on the end of their hyphae. According to the Journal of Wild Mushrooming, hyphae are threadlike, branching structures that make up the body of the fungus.
Microbe World describes one species of fungus, called "Arthrobotrys dactyloides", that actually creates snares to capture prey by forming looped hyphae. The snares are used to trap tiny nematodes. Other fungi live in partnership with other species. Lichen look like plants, but they are actually a combination of two organisms: a fungus and a plant. The plant feeds the fungus, and the fungus anchors and protects the plant. However, even with these unusual species, the basic principle remains the same. Fungi absorb and externally digest their food, whether it is by grazing, trapping it or by being fed by a plant partner.