Wicca, also known as Pagan Witchcraft, is a Pagan religious movement. Its adherents are referred to as Wiccans, though the terms Witches or Crafters are also sometimes used. Developing in England in the first half of the 20th century, Wicca was popularised in the 1950s and early 1960s by a Wiccan High Priest named Gerald Gardner, who at the time called it the "witch cult" and "witchcraft," and its adherents "the Wica." From the 1960s onward, the name of the religion was normalised to "Wicca."
Wicca is typically a duotheistic religion, worshipping a goddess and a god, who are traditionally viewed as the Triple Goddess and Horned God. These two deities are often viewed as being facets of a greater pantheistic godhead, and as manifesting themselves as various polytheistic deities. Nonetheless, there are also other theological positions within Wicca, ranging from monotheism to atheism. The religion also involves the ritual practice of magic, largely influenced by the ceremonial magic of previous centuries, often in conjunction with a broad code of morality known as the Wiccan Rede, although this is not adhered to by all wiccans. Another characteristic of this religion is the celebration of seasonally-based festivals, known as Sabbats, of which there are usually eight in number annually.
There are various different denominations within Wicca, which are referred to as traditions. Some, such as Gardnerian and Alexandrian Wicca, follow in the initiatory lineage of Gardner; these are often collectively termed British Traditional Wicca, and many of their practitioners consider the term Wicca to apply only to these lineaged traditions. Others, such as Cochrane's Craft, Feri and the Dianic tradition, take primary influence from other figures and may not insist on any initiatory lineage. Some of these do not use the word "Wicca" at all, instead preferring to be referred to only as "Witchcraft," while others believe that all traditions can be considered "Wiccan."
Source: Wikipedia, "Wicca", available under the CC-BY-SA License.