There are many magical subjects taught at Hogwarts, each teaches its own pacific area of magic.
Transfiguration is the study of spells used to transform one object into another. It is one of the main subjects at Hogwarts and is taught as a compulsory subject in most years.
The classroom is located on the ground floor leading off the Transfiguration Courtyard. It is a large, light room with cages on either side of the rows of desks (used to house animals before they are transformed into other forms).
In Potions students learn how to brew potions using various magical ingredients and recipes.
Potions Class is located in the dungeons.
Charms is the class where students learn spell which are used to make objects do things.
Herbology the the magical equivalent of gardening. Students have to learn about magical plants ant their uses, but also have to care for the plants as well.
When Harry Potter is at Hogwarts it is taught by Pomona Sprout.
Herbology is taught in the many greenhouses at Hogwarts.