My name is Phyllis Curott, and I'm a Wiccan priestess and the founder of the Tradition of Ara.
Gaia is the ancient Greek goddess of the earth, the great mother goddess. She preceeded the Olympian deities. She was part of the early gods. The Temple at Delphi, in fact, was originally hers, before it was rededicated to Apollo.
She is the earth itself, she is the divine expressing itself through the earth. The earth is the manifestation of the Goddess of the Divine Feminine, and we call her Gaia.
If you're familiar at all with the work of Lovelock, he's discovered, in fact, his theory is that the earth itself, in its entirety, behaves just like a living being, that the total sum of the earth is, itself, a living being and we would refer to her, as he does, as Gaia.