It is used for rotation transmission between the shafts, relative position of which in space is arbitrary.
Yellow bar is connected to the green shaft by a revolution joint.
Yellow bar is connected to the violet shaft by point-on-plane joints
It is not a constant velocity joint, when the input green shaft axis intersects with the output violet one. The video shows case of 15 deg. intersecting angle.
It is a constant velocity joint, when the input and output shafts are parallel.