Wicca is an oath-bound mystery religion, focused primarily on honoring the God and Goddess, while celebrating the cycles of birth, life, death and rebirth - through the passing of the seasons. Though often touted as an ancient religion, Wicca, as it is currently practiced, is relatively modern. Introduced publicly by Gerald Gardner in the early part of the 20th century, it is a mix of witchcraft, ceremonial magic and other older Pagan religions.
In addition to personal spiritual practices, Wiccan rituals are typically celebrated on the Sabbats and Esbats. Sabbats are held on the solstices, equinoxes and cross-quarter days, while Esbats are held monthly at the full moon. Though both the God and Goddess are always honored at these ceremonies, Sabbats (which are solar in nature) relate primarily to the God's journey through the Wheel of the Year, while Esbats (which are lunar in nature) are focused on the Goddess.
Along with the Three-fold Law, Wiccans generally follow some version of the Wiccan Rede. This is often cited as part of a longer poem by Doreen Valiente, but is in fact only eight words long, essentially stating 'An it harm none, do as ye will. Though some take this as a blanket prohibition on causing harm, it does not expressly state that one cannot cause harm - only that if it doesn't cause such, then an action may be taken freely. The deeper meaning to the Rede however, is that that one should always consider their actions carefully before taking them, and be willing to accept the consequences of such actions - particularly if it is an action that may cause harm.
Though many often confuse the practice of Wicca with Satanism, the two have no connection. As a Christian concept, Satan has no place in Wiccan practice or beliefs. Part of the misconception is due to the fact that Wiccans practice Witchcraft, which many Christians see as being "evil." However, as with most things in life, the use of magic is not inherently bad or good - what matters is how one uses it.