There's an old saying that if you ask any ten Wiccans about their spiritual beliefs, you'll get at least fifteen different answers.
Wicca as a religion was introduced by Gerald Gardner in the 1950's (here's a great Biography of him) and was based on his experiences and studies of indigenous cultures magic rituals (or something like that). His tradition was oathbound, initiatory and secret, as in only select people were invited. In the end splinter groups began forming and new traditions were established.
Core beliefs of Wicca
While not exclusive to every tradition, the following beliefs are some of the core tenets found in most Wiccan systems.
Divine in nature: they believe that the divine is present in nature, so nature should be honored and respected.
Karma and Afterlife: the idea of karma and the afterlife being revisited upon us in the next life is prominent in Wicca. The law of three is also a core belief, it in my opinion is a warning from older Wiccans to the newer ones to mind their actions and words. It's said as what you put out will come back to you three fold.
Ancestry: many Wiccans believe their ancestors are watching over them and will commune with the spirit world for guidance and help.
Holidays: are based on the turning of the earth and the cycle of the seasons, Wicca has eight major Sabbats, or days of power, that are celebrated. There are also monthly celebrations called Esbats which are monthly meetings held on the full moon, commonly done for initiations and healing rituals.
Personal responsibility: everyone is responsible for their own actions (this is where the law of three warning comes in) whether magical or mundane, you must be willing to accept the consequences good or bad of your behavior.
Harm none: is a common theme in many Wiccan traditions. It's also common theme many other traditions as well. Harm none, while interpreted differently by each tradition actually follows the concept that no harm should be intentionally done to another individual.
Respect for other beliefs: Wiccans generally avoid discussing other beliefs, and when the subject is brought up they will respect the other beliefs and not be derogatory or rude about it. Wiccan practitioners recognize that others must find their own spiritual path without coercion.
