Witchcraft is one of the many forms of magical practice. A person who practices witchcraft may follow any religion, or may practice no religion at all.
Some Witches may follow Pagan beliefs and view their practice of witchcraft as an important part of their religion, but this is not true of all. I believe Brysing here on this site falls into this category and could answer your questions about religious Witchcraft that is not Wiccan.
Wicca is a very specific modern religion based on the pre-Christian religions of northern Europe with very specific beliefs and practices. Part of Wiccan belief/practice is the practice of witchcraft. One is not Wiccan if they do not practice witchcraft.
So it would be correct to say that all "Wiccans are Witches, but not all Witches are Wiccan."
If you are interested in learning more about Wicca you might want to read through the material at http://wicca.cnbeyer.com/wicca101/index.shtml