Slytherin

Slytherin is one of the four houses at Hogwarts and is generelly considered the evil house. Most Dark Wizards came from Slytherin and Voldemort and almost all of his Deatheaters were in the house of the snake as well. One of the founders of Hogwarts, Salazar Slytherin, was a parselmouth and therefor in the Slytherin shield you see a snake together with the house colours green and silver. Severus Snape is the head of house and the dormitories are in the dungeons with the common room underneath the lake.

Salazar believed that only children of pureblood families should be accepted at Hogwarts that means children from wizarding families only. He left the school after a fight with Godric Gryffindor about this a thousand years ago. He valued resourcefulness and a certain disregard for the rules and the sorting hat describes the students in Slytherin as "cunning". Draco Malfoy is in Slytherin as was his father Lucius at the time when James Potter was attending the school.

There is unfortunately not much we know about the house of Slytherin and about its founder Salazar Slytherin. There is much left to the imagination.