What is a 'buttonhook turn' and why is it preferred over a 'jug-handle turn' for commercial buses making right turns?

1. A turn where you swing wide into the adjacent left lane before turning right
2. A turn where you keep the bus close to the right curb, drive straight into the intersection, and turn late and wide
3. A turn made completely in reverse to ensure the rear wheels do not hit the curb
4. A turn where you swing wide onto the sidewalk to maximize steering angle