Retrograde motion refers to the change of direction of the planets as they wander through the fixed background of the stars. All planets show retrograde motion when viewed from Earth with respect to background stars.
Superior Planets show retrograde motion when they are in opposition, Inner planets Venus and Mercury appear to move in retrograde in a similar mechanism, but as they can never be in opposition to the Sun as seen from Earth, their retrograde cycles occur when they are in lower conjunctions with the Sun. For example, Mars appears to move monotonically in one direction but then suddenly during the time of opposition, appears to move backwards making a retrograde loop. Later it again shows motion in forward direction. Although it actually does not move in opposite direction, following figure illustrates the motion-