What is the meaning of "Fair is foul and foul is fair"?

The line fair is foul and foul is fair in macbeth has alot of meanings and the line is reiterated in the play over and over again though it was paraphrased.
It mainly means that not everything that can be seen is real. Nothing is what it seems. If you see someone smiling it does not necessarily mean he is smiling because he is happy. A smile has many meanings. It can mean the person is planning to do something devious or his smile is simply just a facade. In actualit...