Every deity that has received worship upon this planet exists with the archetypal God and Goddess. The complex pantheons of deities which arose in many parts of the world are simply aspects of the two. Every Goddess is resident within the concept of the Goddess; every God in the God.
Wicca reveres these twin deities because of its links with nature. Since most (but certainly not all) nature is divided into gender, the deities embodying it are similarly conceived. In the past, when the Goddess and God were as real as the Moon and Sun, rites of worship and adoration were unstructured - spontaneous, joyous union with the divine. Later, rituals followed the course of the Sun through its astronomical year (and thusly the seasons) as well as the monthly waxing and waning of the Moon. Today similar rites are observed by the Wicca, and their regular performance creates a truly magical closeness with these deities and the powers behind them.
Fortunately, we needn't wait for ritual occasions to be reminded of the Gods' presence. The sight of the perfect blossom in a field of bare earth can instill feelings rivaling those of the most powerful formal rite. Living in nature makes every moment a ritual. The Wiccans are comfortable in communicating with animals, plants and trees. They feel energies within stones and sand, and cause fossils to speak of their primeval beginnings. For some Wiccans, watching the Sun or Moon rise and set each day is a ritual unto itself, for these are the heavenly symbols of the God and Goddess. Because the Wicca see Deity inherent in nature, many of us are involved in ecology - saving the Earth from utter destruction by our own hands. The Goddess and God still exist, as they have always existed, and to honor them we honor and preserve our precious planet.
In Wiccan thought, the Deities didn't exist before our spiritual ancestor's acknowledgment of them. However, the energies behind them did; they created us. Early worshippers recognized these forces as the Goddess and God, personifying them in an attempt to understand them. The Old Ones didn't die when the ancient Pagan religions fell to upstart Christianity in Europe. Most of the rites vanished, but they weren't the only effective ones. Wicca is alive and well and the Deities respond to our calls and invocations.
When envisioning the Goddess and God, many of the Wicca see Them as well known deities from ancient religions. Diana, Pan, Isis, Hermes, Hina, Tammuz, Hecate, Ishtar, Cerridwen, Thoth, Tara, Aradia, Artemis, Pele, Apollo, Kanaloa, Bridget, Helios, Bran, Lugh, Hera, Cybele, Inanna, Maui, Ea, Athena, Lono, Marduk - the list is virtually endless. Many of these deities, with their corresponding histories, rites and mythic information, furnish the concept of deity for Wiccans.
Some feel comfortable associating such names and forms with the Goddess and God, feeling that they can't possibly revere nameless divine beings. Others find a lack of names and costumes a comforting lack of limitations. If you haven't studied non-Western polytheistic religions or developed a rapport with divinities other than those with which you were raised, start by accepting this premise (if only for the moment): deity is twin, consisting of the Goddess and the God.
They have been given so many names they have been called the Nameless Ones. In appearance they look exactly as we wish them to, for they're all the Deities that ever were. The Goddess and God are all-powerful because they are the creators of all manifest and unmanifest existence. We can contact and communicate with them because a part of us is in them and they are within us.
The Goddess and God are equal; neither is higher or more deserving of respect. Though some Wiccans focus their rituals toward the Goddess and seem to forget the God entirely, this is a reaction to centuries of stifling patriarchal religion, and the loss of acknowledgment of the feminine aspect of Divinity. Religion based entirely on feminine energy, however, is as unbalanced and unnatural as one totally masculine in focus. The ideal is a perfect balance of the two. The Goddess and God are equal, complementary.