Retrograde motion is an apparent change in the movement of a planet, where it appears to move backward in the sky. This phenomenon occurs due to the relative positions and motions of the Earth and other planets, such as Mars or Jupiter. As Earth orbits the Sun, it can overtake these outer planets, creating the illusion of backward motion. This effect is most noticeable with planets that are farther from the Sun than Earth. During retrograde motion, these planets seem to slow down, stop, and then reverse direction before resuming their normal path. This optical illusion is a result of the different orbital speeds of the planets involved.