The Triple Moon Symbol is a popular pagan and Wiccan symbol used to represent the Goddess. It shows different portions of the lunar cycle, with the moon in three phases – waxing, full and waning. First, there is a crescent moon that is in a growing/waxing phase. In the center comes a circle representing the full moon, and finally, there is a crescent denoting the diminishing/waning moon.
Spiritual and religious symbols contain meanings that delve into the deeper reality. The same goes for the Triple Moon Symbol, which is considered representative of all aspects of the divine feminine power – intuition or psychic insight; creative energy; and wisdom & mystery. It indicates the three life stages of a woman.
The waxing moon stands for the Maiden and symbolizes purity, youth, new life, beginnings, rejuvenation, excitement, enchantment, and expansion. The full moon represents the Mother and represents fulfillment, fertility, ripeness, potency, compassion, giving, caring, nurturing, protection and power. The waxing moon represents the Crone and stands for repose, maturity, wisdom, experience, knowledge, understanding, completion, death and rebirth. In its entirety, the symbol is believed to signify the eternal cycle of birth, life, and rebirth.
Also called the Triple Goddess symbol, the Triple Moon icon is commonly seen on the crowns or headpieces worn by the High Priestesses.
source: Ancitent Symbols