Except for one thing. The Wiccan priest who introduced me to Wicca told me quite cheerfully, "All of this is in your head. None of this is real."

It's about celebrating nature, and the feeling of that experience itself. There's nothing to "believe" per se. It's understood to be a framework of metaphors, at least by people who practise it. The above posts show that not everyone gets that.

There's a tradition that when a meal is shared at a Wiccan sabbath, a plate of food is set aside and then left "for the fairies". I once asked if we could come up with an alternative since really the raccoons got to the food before any "fairies" did. The hostess of that gathering rolled her eyes and said, "what, you think I don't know the raccoons have been eating it the whole time?"