Heads and Co-Heads of Houses are the leaders of their respective Hogwarts House. They are responsible for organizing house activities and represent their respective house in the executive board, in addition to the basic responsibilities granted by being on the exec. Heads of House have just as much influence in the exec as Vice President, Secretary, Treasure, and Social Chair, and those titles only grant further responsibilities. You do not have to be a Head of House to hold a position in the executive board. There is at least one Head of House per house every school year, and no more than two. When there are two, they are referred to as Co-Heads of House.