The Goddess is the Universal Mother.  She is most often seen as the Triple Goddess, being the Maiden, Mother, and Crone.  We see her in the waxing, waning, and full Moons. 

As the Maiden, she is young, energetic, carefree and full of life.  She is the virgin girl running through flowered fields in spring and relishing in her youth. 
As she grows older and unites with the God at Beltane, she becomes the Mother.   Comforting, caring, and nurturing, she is the source of life, abundance, and love.  
As she grows old, she becomes the Crone.  Wise, all-seeing, and powerful, she brings with her the forebearing of death, which is also the start of a transition to new life.
Each can be seen in a myriad of Goddess aspects, but the most used are Artemis and Diana, Cerridwen and The Great Mother, and Hecate.

Many symbols are used in Wicca to represent the Goddess, such as the cauldron, chalice, mirror, necklace, seashell, pearl, hag stone, silver, emerald, five-petalled flower, and the list goes on.
She has dominion over Earth, sea, and Moon.  Creatures sacred to her include the rabbit, horse, own, cat, dog, bat, cow, goose, dolphin, lion, wren, spider, bee, lion, scorpion, and bear.

The Goddess has been depicted as a huntress running with Her hounds; a celestial deity striding across the sky with stardust falling from Her heels; the eternal Mother heavy with child; the weaver of our lives and deaths; a Crone walking by waning moonlight seeking out the weak and forlorn, and as many other beings.   But no matter how we envision Her, she is omnipresent, changeless, and eternal.