Witch
A witch is a female practitioner of witchcraft. In modern times this has also included Wicca.
In the past many people accused of witchcraft were burnt at the stake or executed in other ways - it is generally agreed that most of these people knew nothing of witchcraft, and were witches only in the imaginations of those accusing them. It is interesting to note that one-quarter of those executed for witchcraft were men. In Exodus 22:18 the Old Testament specifically bans witchcraft under penalty of death.
The most famous episode is the Salem Witch Trials of 1692 in Massachusetts, in which numerous accused witches were hanged (none were burned). A famous British case was the [Pendle Witch]] trials of 1612 AD.
In 19th century romanticism, witches and the occult became popular figures of novels and fairy-tales. Most of the times they were of evil and dangerous character, but there are also examples of benevolent character. At about the same time they became popular carnival figures.
Modern Usage
The term witchhunt is also used to denote a political crusade against a particular group.