What does it mean when a planet is in retrograde?

When a planet appears to move backward in the sky (retrograde), its energy is said to turn inward or become more reflective. Mercury retrograde is famous for communication and technology issues. Venus retrograde affects relationships and values. Mars retrograde impacts energy and motivation. Outer planet retrogrades are longer and affect generations. Retrograde periods are actually opportunities for review, reflection, and revision in the areas that planet governs.