Witches are highly feared individuals. They have connections to shades. If they are 'tainted', they are considered beyond saving and are killed. Usually by a hunter. After the events in Spell Sword and Pact it becomes clear there's a distinct difference between wood witches and shade witches.
Hood Episode One
The Wolf says he rarely encounters an actual witch. One can surmise that certain undiscerning individuals in the world falsely accuse others of being witches, no doubt in order to gain something from the demise of those accused.