Each planet has a specific influence and governs a certain area.
Nine planets, the wanderers, revolve around the Sun.
The angular relationship between planets, sensitive points, or house cusps in a horoscope. Aspects can indicate harmony or challenge.
This is the optical illusion of a planet moving backward, created by variance in rates of speed of travel between different planets in the solar system as we observe them. Retrograde cycles bring a need to reconsider, revise, and rest. For deeper insight, think of all the words beginning with "re". When retrograde, planetary energies manifest in unexpected ways. They can be softer or blurred while retrograde. Retrograde motion is not unfavorable, just different.
The sign of the Zodiac in which the Sun is located at any given time.
A planet is void-of-course after it has made its last aspect within a sign, but before it has entered a new sign.