What does eye of newt mean in Macbeth?

In William Shakespeare's play "Macbeth," the phrase "eye of newt" is mentioned as one of the ingredients in the witches' brew. It is a metaphorical reference to the use of various parts of animals and plants in witchcraft and magic.

The "eye of newt" specifically suggests the use of the eye of a newt, a type of salamander, in the witches' potion. This is not a real ingredient used in witchcraft, but it adds to the mysterious and otherworldly atmosphere of the play.

In the context of the play, the witches' brew is meant to be a potent and transformative concoction that will aid Macbeth in his quest for power. The use of seemingly strange and exotic ingredients, such as the eye of newt, reinforces the idea that the witches are dealing with dark and supernatural forces.