Retrograde and direct motion
Direct motion is the motion of a planetary body in a direction similar to that of other bodies within its system, and is sometimes called prograde motion. Retrograde motion is motion in the opposite direction. In the case of celestial bodies such as the retrograde Carme group of moons, such motion may be real, defined by the natural rotation or orbit of the body.
Every so often a planet seems to change direction and go the other way for a short period of time (in relation to the fixed stars), making a loop or squiggle in its track before carrying on as normal. This apparent retrograde motion, however, is seen because the Earth is moving. It is only seen when outer planets -Mars to Neptune are near opposition.