Hogwarts is divided into four houses, each bearing the last
name of its founder: Godric Gryffindor, Salazar Slytherin, Rowena Ravenclaw and
Helga Hufflepuff.

The houses compete throughout the school year, by earning
and losing points for various events, for the House Cup (correctly answering a
question in class, for example, may earn five or ten points; lateness to class
may cost ten points). Each house also has its own Quidditch team that competes
for the Quidditch Cup. These two competitions breed rivalries between the
houses. 

Houses at Hogwarts are living and learning communities for
their students. Each house is under the authority of one of the Hogwarts staff
members. The Heads of the houses, as they are called, are in charge of giving
their students important information, dealing with matters of severe
punishment, and responding to emergencies in their houses, among other things.
Each year, year level groups of every separate house share the same dormitory
and classes. The dormitory and common room of a House are, barring rare
exceptions, inaccessible to students belonging to other Houses. 

In the early day of Hogwarts, the four founders hand-picked
students for their Houses. When the founders worried how students would be
selected after their deaths, Godric Gryffindor took his hat off and they each
added knowledge to it, allowing the Sorting Hat to choose the students by
judging each student's qualities and placing them in the most appropriate
house. The student's own choices may affect the decision along with the
students personality traits. Each house represented an aspect of the school the
four founders wanted to bring out in new students. In the following chapters will have more details on the houses themselves.

"We must unite inside her, or we'll crumble from
within."

—The Sorting Hat