Wicca is not the same thing as Witchcraft. There are similarities and there are differences, a few of which I plan to lay out in a moment. I will agree with most Witches and say that the two terms should not be interchanged, as they commonly are. It would be like calling a Roman Catholic a Protestant or a Baptist - they believe in the same basic tenants, however they go about it in a totally different way. One thing to remember when you read this is that these are generalities about Wicca and Witchcraft. Not all Wiccans follow the same beliefs, and not all Witches follow the same beliefs as other Witches.
Most Wiccans follow the Wiccan Rede as one their basic tenants. This is a poem written by Adriana Porter and Lady Gwen Thompson, sometime in the 20th century. The shortened version of this is "An it harm none, do what you will", which is pretty much self-explanatory. Along the same lines, (most) Wiccans also follow the Law of Power or Three-Fold Law. This is rather along the lines of Karma - whatever force you send out will return to you three times as strong. Witches, on the other hand, do not follow any such redes, rules or tenants - unless they are a specific part of the Tradition they follow. From what I understand most find the Three-Fold Law illogical.
The other main difference between Wicca and Witchcraft, is how magick is practiced. Wiccans generally cast a circle before doing any magickal rites or rituals. This merely consists of creating a sphere of energy that surrounds yourself and anything that will be used in the rite or spell. Whereas some Traditions of Witchcraft may use circle casting occasionally, to most Witches all space is sacred and circles are not needed for rites.
Wiccans tend to place heavy emphasis on rhyming chants and ceremony (or ritual), such as having corresponding colours and herbs for a certain spell - or casting a spell on a Tuesday when the moon is full. Witches, however, more often use whatever they have when they feel the time is right.
Those are a few of the differences, and hopefully have helped to straighten out the interchangeable Witchcraft/Wicca.
