There are many Deities worshipped under Pagan belief structures. Some simply believe in One Goddess; some believe in one God and Goddess; and others believe in multiple Gods and Goddesses.
Some practitioners only follow one specific pantheon, others a mix of several.
There are no right or wrong paths or beliefs within the Pagan Community. Your individual beliefs and faiths are no less valid than any other person's. The key is that it is what YOU feel connected with/to and that you remain true to those beliefs.
The universal symbolism for the Goddesses is the Moon. The symbol incorporates the Waxing, Waning and Full Moon phases. Many feel that the Triple Moon also symbolizes Maiden, Mother and Crone - the 3 aspects of the singular Goddess.
Another common symbolism for the Goddess is a womanly form with arms raised, hands clasped over her head. Many times a spiral is drawn in her stomach/womb area. Occasionally both the triple moon symbol and this one will be combined into one symbol.
While these symbols are by no means the only symbols used within the Pagan community, they are some of the most common and most recognized.