What exactly DO Wiccans believe?

A complete discussion of the Wiccan Religion would be beyond the scope of a limited forum such as this, but, in a nutshell:

Wicca is a Neo Pagan religion founded in 1939 by Gerald Gardner, and expanded by Doreen Valiente and Alex Sanders, as an attempt to recreate the Religious Practices of preChristian Western Europe. It drew heavily on the Western Mysteries tradition that comes to us through the Middle Ages and dates back to the Pythagorans of Ancient Greece, it was the Pythagorans who first adopted the Pentagram as a religious symbol, and the pentagram is now the accepted symbol of Wicca, as is a cross or crucifix for Christianity. Wicca is a fertility oriented Duotheistic faith built around a God and Goddess who represent the active and passive creative forces of nature. The guiding philosophical principle is known as the "Wiccan Rede", "So it harm none, do what you will."

Wiccans are polytheistic. Most commonly old pagan gods are the ones being worshipped. Many, although certainly not all, Wiccans believe in creatures called elementals. Most Wiccans work fairly extensively within an elemental framework: they believe in the four physical elements and incorporate them into ritual, even if they do not believe in elemental entities. (for example, they work with fire, water, air and earth even if they don't believe in beings called earth elementals.)

Wicca is a Pagan religion. Wiccans connect with the god and goddess and are usually (always?) Polytheistic. Often they have a great reverence for nature and are active in environmental causes.

I will star your post so that my Pagan friends can answer more fully.

I've been told that this website is a reliable one:

http://www.witchvox.com/

The best online resource for learning what Wicca is, and is not, can be found here:

http://wicca.timerift.net/wicca101/index.shtml

There is also a great recommended reading list there if you want to learn more.

What exactly do we believe about what?

I believe in the gods, yes. I do not believe in elementals, they come from Christian mythology.