A running back (RB) is a member of the offensive backfield in gridiron football. The primary roles of a running back are to receive handoffs from the quarterback to rush the ball, to line up as a receiver to catch the ball, and block. There are usually one or two running backs on the field for a given play, depending on the offensive formation. A running back may be a halfback (in certain contexts also referred to as a "tailback" — see below), a wingback or a fullback. A running back will sometimes be called a "feature back" if he is the team's starting running back.