Professor Salazar Slytherin was a pure-blood wizard of medieval times. He was a Parselmouth (a wizard with the rare ability to speak with snakes) and skilled at Legilimency. He was one of the four founders of Hogwarts School of Witchcraft and Wizardry and the former best friend of Godric Gryffindor, a fellow founder. Slytherin didn’t trust Muggle-born students, and he expressed his opinion not to accept them at Hogwarts. However, when the other Hogwarts founders didn’t agree, Slytherin created the Chamber of Secrets, concealing a basilisk inside. Afterwards he left the school, never to return. He died sometime in the Middle Ages.
Like Rowena Ravenclaw and Godric Gryffindor, Salazar Slytherin appears to have carefully selected members of his own House. According to Albus Dumbledore, the qualities which Slytherin prized in his “handpicked students” included resourcefulness, cleverness, determination, and a certain disregard for the rules, along with the ability to speak Parseltongue. He also selected his students according to cunning, ambition, and blood purity. His House within Hogwarts is symbolised by a serpent, with House colours of green and silver. [x]