The description of retrograde motion in FE Wiki seems to have one small flaw in it. The top image is indeed very reminiscent of what retrograde motion looks like in the sky. But the schematic below shows the Sun in orbit around the northern hub. Given that the Sun seems to dissect the retrograde loop of the planet, that surely means that the Sun would be in the direct line of sight during the loop and therefore rendering it invisible to us.
Retrograde motion happens during the period before and after a planet further out from the Sun than Earth reaches opposition. The Earth is orbiting the Sun in about half the time that Mars does. (365.35 days v 687 days). So for a period of time, as seen from Earth the planet appears to move backwards against the background stars. The start and end times of the backward movement are known as stationary points in right ascension. At no point in this model does the Sun ever get directly between the Earth and the planet.