An explanation of prograde and retrograde planetary motion

Until it was explained to me I thought that when people referred to ‘prograde’ movement of a planet, they meant that it was moving, in general, with the apparent movement of the background stars, slightly further west as viewed on consecutive nights, and that, consequently, retrograde movement was in the opposite direction, to the east. As we are relatively distant from but moving towards, say, Mars, it moves steadily prograde, west to east when compared with the background stars, then as we really start to catch up it seems to slow down and stop, reaching a stationary point against the background stars, then it seems to reverse direction and we say the planet has started retrograde motion, east to west. It is just the orbital motion of Earth that makes it, and any of the outer planets appear to move first west to east, prograde, then east to west, retrograde, and finally back to prograde again.

Source: www.popastro.com