It's a question of belief. Wicca is a religion, not simply a magickal system. The Witches' Voice
is a good resource site (for more than Wiccan beliefs.)
Here are some bullet points that I've used when talking to the local media:
Wicca is a pantheistic/polytheistic, nature-centered religion.
Wicca is an experiential, rather than revealed, religion.
Wiccans acknowledge and worship an immanent, rather than transcendant, divine, usually represented as a God and Goddess.
Wiccans strive to live in harmony with, rather than in mastery over, Nature.
Wicca stresses personal responsibility and individual knowledge of the Divine rather than adherence to specific religious law.
Wiccans live by the Wiccan Rede: An it harm none, do as you will.
These aren't exhaustive, of course (and some are given more weight than others depending on the tradition), but they'll give you some idea of how our faith is structured.