The Hogwarts Grounds are part of Hogwarts School of Witchcraft and Wizardry and surround the Hogwarts Castle.
From the Story
"The expansive Hogwarts grounds, which lead to the Forbidden Forest, include Herbology greenhouses, a broomshed and a lake, as well as a Quidditch pitch. Hagrid's hut and vegetable patches lie near the edge of the Forbidden Forest. The extremely dangerous Whomping Willow stands at the bottom of one of the castle's gently sloping lawns."