Traditionally, his role was as "second receiver" i.e. the half-back/scrum-half was first receiver (from the dummy half) and he would pass it to the 5/8th who would the distribute it to the outside backs. In the modern game the distinction between half-back and 5/8th has disappeared to some extent. Some teams still play them as separate positions but others play one "half" on each side of the field. Usually the half-back is the more organising member of the halves pairing and the 5/8th the more creative one. Often this is because the 5/8th stands deeper in the attacking line and there has more time to think about his attacking moves. Also, traditionally the half-back would feed and receive the ball from the back of the scrum (hence the name "scrum-half") but the way scrums are played these days the half-back could be with the outside backs or even in the scrum.