Witches were women who were said to worship the Devil and carried out his evil wishes. They would often be said to have an assistant (known as their familiar) who had been sent to them by the devil. In some illustrations, these appear as strange supernatural creatures, but in reality pets such as cats were classed as being familiars
The majority of those accused of being witches were single, old women who stood out or were seen as different. Some people found those seen as different as threatening. These women would find it far more difficult to defend themselves in a trial situation.
Witches were blamed for many different things, from crops failing, to someone falling ill and dieing. Today we have scientific understanding of the world around us, which they did not have in the past. Witches were used to explain a range of different phenomena that would otherwise be unexplainable.