Planets defined represent 'the What' of astrology. What type of celestial energy is manifesting itself through which particular heavenly body? (Taken from Alan Oken's Complete Astrology)

In this introduction, I'll be focusing on the core planets for the 12 Sun Signs and not the asteroids. There are 10 core planets. Remember, when casting natal charts, they are geocentric, meaning that earth is the central vantage point.

Sun Vitality, the will, who you are, your self-image, our sense of identity, the individuality, the point at which an individual integrates all his or her various talents and energies (as indicated by all the natal planetary positions) into one creatively functioning being. Rules Leo.

Moon How we respond emotionally, intuition, feeling, security, sensitivity, how we nurture, our receptive nature, describes our mother, our desires, tells what our emotional needs are. Rules Cancer.

Mercury How we think and communicate, the mind, ideas, interests, intellect, reasoning, logic, expression, speech, writing, nervousness. Rules Gemini and Virgo.

Venus Who we look for in relationships, how we handle money and possessions, love, pleasure, romance, art, profit, social grace, poise and manners.

Mars How assertive we are, describes physical activity, competition, how we express anger, describes how we take action and the type of action we take, sexual drive, courage. Rules Aries.

Jupiter How we expand and grow, where we have abundance, describes the type of opportunities we have, optimism, enthusiasm, wisdom, extravagance, our spiritual concepts, self righteousness, our search for knowledge. Rules Sagitarrius.

Saturn Shows where we need to take responsibility, where we feel inadequate, discipline, structure, seriousness, caution, blockage, delays, maturity, fear, guilt, inhibitions, restriction, concentration. Rules Capricorn.

Uranus Shows where we need to have freedom of thought and action, eccentricity, enlightenment, originality, unusual, unpredictable, revolutionary, independence, upheavel, breaks up old patterns, awakening, the higher mind. Rules Aquarius.

Neptune The dissolver, tells us about our spiritual values, the desire to connect with our Source, spiritual love, kindred souls, vision, dreams, devotion, inspired creativity, imagination, confusion, ungrounded, nebulousness, illusion, idealism, sacrifice, serve others, charitable, sympathy, compassion. Rules Pisces.

Pluto Teaches us about our personal power, transformation, the cycles of birth and death, regeneration, destruction, rejuvenation, intensification, investigation, obsessiveness, manipulation, eliminates or purifies that which is no longer necessary for soul growth, integration of one's dark side. Rules Scorpio.