A running back (RB) is an American and Canadian football position, a member of the offensive backfield. The primary roles of a running back are to receive handoffs from the quarterback for a rushing play, to catch passes from out of the backfield, and to 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) or a fullback.