This is the famous "stepping feet" illusion from Prof. Michael Bach. The yellow and blue "feet" appear to be stepping, and even out of step with one another, but this is an illusion caused by the vertical grid they are walking across. At the right side of the gif, the grid vanishes and you can see the feet were moving at constant speed  all along.

Which way are the black/white dots rotating around the centers of the two figures? Can you, by concentrating, make the direction of motion reverse? If you relax your eyes does it appear for an instant that different dots in the same figure are rotating in opposite directions?!? Try concentrating on the yellow dot. How do the rings rotate? Now concentrate on the red dot. Now how do they rotate?

The blue/yellow rings are completely at rest within the frame of the image, but if you take the arrows as your cue, you will see illusory motion of the rings in the direction of the arrows!