English: This animation helps to spatially visualize the nodes of orbits of two planets, for example the Earth and Venus. The two celestial bodies orbit around the same object (the Sun), and the angle of their planes is not zero. These planes intersect each other in a straight line, passing through the central object, and this line designates the two "nodes" of each elliptic trajectories.
(You should see this animation infinitely looped with a short break.)