Here are a few definitions:
Wicca is Experiental
Wicca is an experiental religion. What this means is that how Wicca works in a person's life is heavily influenced by that person's experiences. There is no central church of Wicca, and no Wiccan Bible, Torah, or Koran to outline the beliefs, rules, and teachings of the religion. You learn Wicca by living it. Your experience tells you what is true, what works for you, and what you believe. We walk this path somewhat like scientists, testing things out and shifting our beliefs according to the outcome.
Once you have experienced something, you "own" it. It is part of you. You understand it at a level that you couldn't by just reading about it. Therefore until you have performed Wiccan rites or tried to do a spell, you have no frame of reference for it. Wicca is a religion where actions truly do speak louder and more powerfully than words.
Wicca is a Mystery Tradition
There are certain spiritual experiences that are nearly impossible to put into words. Many of them have to do with big topics such as death, love, deity, nad birth--things that are core to our existence as humans and yet otherworldly at the same time. If you've ever had a transcendent moment where you just knew that deity was real or you felt particularly connected to nature or the cosmos, as if every bit of you were a part of it, you have probably touched the mysteries. Mystery religions are those that create a setting or a venue where people can have an immediate experience of the reality of the divine. These paths teach that there are things that are beyond the reach of our five senses, but are nevertheless integral parts of us that we can touch directly, although the method will be different for each of us.
Each religion has its own mysteries, or revelations. Some of the Wiccan mysteries--for example, the interplay between the God and Goddess--are mirrored in our sabbat rites. When we participate in the rites, we "act out" what is happening on a cosmic level, beit the change of seasons, the union of the God and Goddess, or any other of a number of Wiccan mysteries, and for that moment we are aligned with the gods.
Some Wiccan mysteries unfold during meditations or dreamwork. Still others come during an "Aha!" moment when a Wiccan has been walking the path for a while, and suddenly important teachings click into place. Wicca, with its focus on natural cycles and emphasis on meditation and psychic abilities, provides many opportunities to touch the mysteries of the divine and the cosmos.
Wicca is European Shamanism
One definition of a shaman is a person who enters an altered state of consciousness in order to take a spiritual journey to retrieve information, heal, work magick, tell the future, or commune with the dead. A shaman is more than a medicine man or a magician, although he or she is often both of these things; a shaman may also be a priest, mystic, and psychopomp (one who can move back and forth between the worlds of the living and the dead).
The concept of the world tree exists in one form or another in cultures across the globe. The world tree is a symbol for the connection between the spiritual realms and earth. The roots of the tree lie in the underworld, the trunk is the human material world, and the branches and leaves are the heavens or celestial realms. The tree can be "real" or a metaphor. The shaman travels up and down the world tree and between the spiritual and earthly realms to perform his or her tasks for the tribe or group. Shamans use many techniques to "travel" the world tree, including trance, shapeshifting, and magic.
A shaman could be "made" if he or she went throught a shamanic crisis--an event so traumatic that it changed his or her life irrevocably. The shamanic crisis could come on naturally, such as with a severe illness or near-death experience. It could also be induced from the outside by an initiation ceremony or trial.
Wicca incorporates a lot of these ideas. Wiccans are taught to be in tune with their psychic abilities. Magick circles, the sacred space of Wiccans, are said to be "between the worlds," and Wiccans "travel" between the worlds to meet the gods, get information, and heal. Wiccans often enter ecstatic or trance states in order to work magic or commune with the divine. Many Wiccans have life-altering experiences that lead them to the Wiccan path, and Wiccan groups often initiate new members in a symbolic death and rebirth ceremony meant to provide a mini-shamanic crisis and shift the initiate's perspective.
This death and rebirth stuff may sound frightening, and frankly, sometimes it is, but it is not negative or dark or bad. It is meant to spur us to overcome our fears, step into our power, and take charge of our spiritual paths, which is difficult to do if nothing in our lives ever challenges us.
Wicca is a Magical System
There is more than one kind of magick. There is everyday magick, where you do spell work for things like finding a new job or protecting your home. Wiccans make use of this type of magick all the time. But there is also the kind of magick that you use to manifest your own personal power and divinity. In essence, it's working your will to find your purpose in life and align with your higher self. The thing to know is that Wicca is a framework in which to work these two types of magick.
If you chose to walk this path, your Wiccan experience can be pagan, experiential, shamanistic, mystical, magickal, or all or none of the above, but the one thing it certainly will be is your own. Wicca, from any angle, is a path of empowerment and personal growth. Like many things in life, Wicca is what you make of it. The joy--and the challenge-- is discovering what it will make of you