Parseltongue is the language of serpents (as well as other magical serpent-based creatures, like the Runespoor and Basilisk) and those who can converse with them. An individual who can speak parseltongue is known as a Parselmouth. It is a very uncommon skill, and is typically hereditary. Nearly all known parselmouths are descended from Salazar Slytherin with Harry Potter and Herpo The Foul two being notable exceptions (although Harry Potter was not a true parselmouth).