The astronomical explanation for retrograde motion starts with understanding that the planets in our solar system orbit the Sun at different distances and speeds. While we orbit the Sun ourselves, we can observe the other planets moving across our sky, following their own paths.
Sometimes, it can appear (from our perspective) that a planet has abruptly switched directions and has started to move in reverse across the sky. This is, of course, an illusion caused by the position of Earth in relation to that of the planet, since a planet in orbit always travels in one set direction and can’t suddenly reverse course. This is why we call the phenomenon apparent retrograde motion, as it only looks like the planet is moving backward (“retrograde motion”)!