What is what does fair is foul and foul is fair mean?

"Foul is fair and fair is foul" is a quote from Shakespeare's play Macbeth. It is spoken by the three witches who serve as the catalyst for the events of the play. This quote reflects the theme of ambiguity and moral confusion that runs throughout the play. In essence, it means that good may appear bad and bad may appear good, suggesting that appearances can be deceiving and one should not always trust their initial perceptions. The quote sets the tone for the dark and twisted events that unfold in the play.