Let's start with looking at what we mean when we talk about "deity". Obviously, we're talking about Gods, but there are different ways Wiccans look at the nature of the Gods. Some believe that all Gods are aspects of one universal "Male" energy, and all Goddesses are of a universal "Female" energy (duotheism, or "soft" polytheism). In that respect, the various Gods and Goddesses are all just "personalities" of these energies. Some even go a step farther and believe that the Male and Female energies are halves of one neutral Universal energy, a sort of monotheism or pantheism. (Pantheism is the belief that all is sacred and divine. See http://members.aol.com/Heraklit1/faqs.htm for more information.)
Other Wiccans, myself included, believe that the Gods and Goddesses are separate entities. I like to think of them as a species on another plane of existence ("hard" polytheism). Each is unique, though there are similarities between cultures just as there are similarities between humans. Interestingly, there is room in Wicca for both views, as well as others. It doesn't really matter how we theorize about the nature of deity. This makes for some wild and interesting theological discussions at times.
Take a moment to think about what you believe about deity. Which of the theories do you like the best? It's an interesting line of thought. It took me a long time to figure out how I felt about the Gods. While I'm polytheistic now, I wasn't always, and I may not be in the future. We're never really going to know the true nature of the divine, and perhaps we aren't meant to. Perhaps this is another one of those Mysteries: though we can't truly know the nature of the Gods, we know they are there. We can feel their presence in our lives. Sometimes we have to look very hard, and sometimes it's so obvious that they beat us over the head.
In Wiccan ritual, we worship a God and Goddess. Some folks choose (or are chosen by) one pair; others work with many different pairings. There isn't a right or wrong way to go about it, but it's good practice to at least understand who you are calling to your aid and why. I have two main deities I work with, Bridget and Loki, but I've also worked with various others in group rituals. This is another interesting thing about Wicca: although various Wiccans and groups focus on specific Gods, there aren't any "universal" Gods of Wicca. We all aren't worshipping the same pair.
