As a modern, made-up religion, it tends to serve its adherents well, since they pick whatever tenets they need to enhance their spiritual life and get them through the night (it's alright, it's alright).
Wiccans range from those who self-identify and loosely follow traditions they imagine to date from pre-Christian European cultures, to those who join small groups ("covens") and sacrifice Christian babies to Satan while chanting backward runic hymns in order to appease Him and gain unearthly powers.
It is well that the reader be advised to be respectful of Wiccans should they encounter any, since they can turn you into a newt (and back again) with the bat of an eyelash. Or, they can turn you into a bat with the eyelash of a newt. Basically, you don't want to get involved in such an identity edit war. The original author of this claptrap is probably already undergoing multiple baramin enemas as a result of even thinking this stuff, let alone writing it down.
It should be noted that there are many Wiccans, particularly traditional Gardnerians, who get really pissy if anyone not in a traditional coven uses the term. They are also irritated by the tendency to refer to "New Age" ideas as part of Wicca. Nevertheless, covenless "solo practitioners" are probably very common, due to the wide availability of books of varying "authority" on Wiccan practice.
For the record, Wicca is claimed as a derivative of the word "Witta," a supposed Gaelic term meaning "wise one." But, some silly writers have tried to claim it is Anglo-Saxon for "front". (Hint: It's not.)
Wiccans usually believe that the world is divided into two planes, a magical plane and an earthly plane. Most wiccans believe in a god and a counteracting goddess, much akin to yin and yang. A common tenet is that "whatever you send away in either plane will come back to you."
Wiccan ethics are summed up in the Wiccan Rede, a pithy, archaically phrased statement that reads
"An it harm none, do as thou wilt."
The exact origin of the statement is unclear, having only appeared in wide circulation in the 1960s, but it is fundamentally a combination of the Golden Rule and Aleister Crowley's "Do as thou wilt shall be the whole of the law".
Some humanists find it a very nice summation of ethics without divine principles in general - though they'd most certainly have a problem with the magic and certain beliefs of the Earth-worshiping hippie nonsense variety.