For witches our Goddess has three aspects, the Maiden, the Mother, and the Crone. Following the three stages of life a woman passes through. Different stages depend on the time of the year and phases of the moon.
The Maiden Goddess is the virgin goddess in her youthful form. She represents youth, enchantment, and promises of new beginnings. She is represented by the waxing moon. Her marriage to the God is on Ostara, in 9 months from Ostara she becomes the mother. I call her Hebe. She represents the youthful, virginal early years of a woman's life.
The Mother Goddess is the goddess who is full with the God's child. She represents fertility, sexuality, power and life. She is represented by the full moon. She gives birth to the young God on Yule. I call her Hera. She represents a woman's fertile years, the years when she can carry life within her body.
The Crone Goddess is the final phase of the Goddess before she begins as the Maiden again. She represents wisdom and death. She represents endings. She is represented by the waning moon. She becomes the Maiden again at Beltane. I call her Hecate. She represents the menopausal phase of a woman's life, or the time when she is wise with years but no longer able to bare children.
The triple phase of the Goddess represents the three phases of life that a woman goes through. Properly invoking the right aspect of the Goddess helps to increase the ritual power.