The exact number of cells in fungi isn't known, but fungi are multicellular, meaning they are made of more than one cell. Most fungi with single cells are in the yeast family and are used in baking and bread making.
Multicellular fungi are composed of filaments called hyphae and are classified as heterotrophs. Being heterotrophs means that fungi, unlike many other fauna, cannot produce their own energy through photosynthesis. Fungi instead absorb nutrients from the matter around them. The fungi's hyphae spread through the food and release enzymes that break down the food into substances that the fungi can easily absorb.