lilyevane:

Houses at Hogwarts were both the living and learning communities for its students. 
   Each year’s group of students in the same house shares the same dormitory and many          classes. The houses compete throughout the school year, by earning and losing points for               various activities. The house with the most points wins the House Cup. Each house also has its own Quidditch team that competes for the Inter-House Quidditch Cup.