Technically this is not quite correct or complete, but
It had an agitator set on an eccentric mounted in a wheel below the tub. When the motor turned in one direction, the agitator made an off center circle in the tub. With the big fins, it moved the water and fabrics in a circle as it turned over the load. When the motor reversed for spin, the whole mechanism, including the tub, turned and the agitator was off-center, looking like the tub was out of balance, but it was not.