About Mars
What is a retrograde motion?
Occasionally, it is spotted from Earth other planets often travel in the opposite direction (backwards), however, this is just an illusion that we see because of the movement of the Earth and the planets orbiting the sun. Nevertheless, the direction of the planets in which they travel does sometime change. This illusion is created when Earth passes over a slow-moving planet.
Mars' retrograde motion
Retrograde motion is different from retrograde rotation. Earth orbit speed is 24% further and faster than Mars' speed. Consequently, Earth always over-takes Mars during its orbit. When Earth is catching up to Mars, we see that both planets are traveling in the same direction, anticlockwise. But as Earth is faster and it over takes Mars it creates the illusion that it is traveling backwards, whereas it's just slower than us.
Example:
You are travelling on a motorway, which has many lanes. Your car is faster than others . There is a car ahead of you but in a different lane. While you are over taking the slow car it seems like it is going backwards . This illusion is only created just as you travel past it. But after a few seconds after you have passed by it, now you see that it is travelling in the direction is was before (same as yours).