Wicca is a modern religion based on the pre-Christian religions of northern Europe. It is a polytheistic religion in that its followers believe in the existence of many different Gods and Goddesses. Here are some good links to sites that will explain it better for you (don't forget to delete the gaps in the URL or it won't work correctly):
I've been a practicing Wiccan for nearly 30 years. If there are some specific questions you have about what Wiccans do or believe I'll be happy to try to answer them for you.