There is a Moon goddess in almost every culture, although when presented on the image of a pentacle it is probably representing a triplicity Goddess of either Celtic or Greek origin. Moon triplicity goddesses represent the phases of the moon – waxing, full, and waning – personifying each in their own way. The goddess of the waxing moon (which is the moon growing brighter from the new moon to the full moon) is seen as a Maiden; the goddess of the full moon is seen as a Mother; the goddess of the waning moon (the moon growing darker from the full moon to the new moon) is seen as a Crone.
The Triple Goddess of Greek origin includes Selene (Maiden), Diana (Mother), and Hecate (Crone), although there is some controversy as to whether it is Diana or Selene who represents the full moon. It is also said that Hecate herself is a Triple Goddess of the moon and that she moves from a young maiden, into a mother, and then a crone throughout the cycle of the moon every month.
The Triple Goddess of Celtic origin is The Morrigan: Badb (Maiden), Macha (Mother), and Nemain (Crone). The Morrigan are also a triplicty of war.
The crescent moon that the goddess on your pendant is holding represents either the waxing or waning moon, while the circle enclosing the pentacle can represent the full moon.
The waxing moon is a time of new beginnings and growth (the Maiden).
The full moon is a time of empowerment and completions (the Mother).
The waning moon is a time of cleansings, releasings, and endings (the Crone).
This pendant can represent and/or be used for all of these things. Anytime you start a new project, decide to end a bad habit, or doing anything of importance or change in your life, wearing this pendant and putting your energy and faith into it will make you and your efforts stronger.