Here's why:

* Structure: Mushrooms are the fruiting bodies of a much larger fungal network called a mycelium. The mycelium is made up of a network of thread-like structures called hyphae, which are interwoven and form a complex, multi-cellular structure.

* Function: The mushroom is responsible for producing spores, which are the reproductive units of the fungus. The mycelium, on the other hand, is responsible for absorbing nutrients from the environment.

While most mushrooms are easily recognizable, there are many other multi-celled fungi, including:

* Molds: These are fungi that grow on surfaces, such as food or walls.

* Yeasts: These are single-celled fungi that are responsible for the fermentation of bread and alcoholic beverages.

So, while mushrooms are a common example, they are just one of many types of multi-celled fungi that exist in nature.