Wicca is the largest of the Neopagan religions. Wiccans have great reverence for the Earth and for their Goddess and her consort, the horned God. Their main rule of behavior is the Wiccan Rede which forbids them from harming people, including themselves, except in some cases of self-defense.
Many, perhaps most, are solitary practitioners. Others form small groups of believers, called covens, groves, etc. Because of centuries of religious propaganda and misinformation, many conservative Christians, and others, associate Wiccans with Satanists even though the two belief systems are as different as Christianity and Atheism.
They estimate there is over 750,000 Wiccans follwers in the United States. That would make Wicca the 5th largest organized religion in the United States, behind Christianity, Islam, Judaism, and Hinduism. However it is virtually unknown by the general public. This is because almost all Wiccans hide their religious beliefs and practices. Those who allow their faith to be known publicly are very heavily persecuted.