Mycology focuses on studying on not just mushrooms but fungi, yeasts and molds. It tries to understand it's structure, reproduction, and classification. It covers many aspects including their function, genetics, ecology and many more applications. Mushrooms and fungi are a lot more inteligent than one might think. Going so far to even have their own type of world the way the animals might have their own or even plants. Which is interesting because fungi is far more closer to human beings than plants.
There is a lot you can tell by the very finest details of a mushroom / fungi specimen. Referencing the diagram, you must take these details when trying to identify a mushroom because even the difference in details will change what you make think you know. Which is why it is important to take note of every single detail when you look at a mushroom.