How do mushrooms grow?
The mushroom part we can see above ground is actually just the reproductive body of the fungus at large. It produces billions of spores (kind of like seeds or pollen) that are spread throughout the environment. Once these spores germinate they start to grow a fine filament called hyphae. When multiple hyphae are growing together they form a network that is called mycelium that branches out in every direction!
The mycelium is the vegetative body of the fungus, and it will continue to expand and grow into the tree, soil, or given substrate specific to the fungus. The mycelium uses enzymes to digest its substrate and to absorb the nutrients into its cells. Once the conditions are right, a fruiting body will develop from the mycelium. Fruiting body is another term for mushroom ;) As the fruiting body matures, it will produce spores and eventually release them.
And there we have the cycle of mushroom life!