The Law of Cause and Effect basically says this, what we put out energetically into the universe, will come back to us. And the example of this would be, when you continuously have an unkind thought or word about someone and allow it to permeate out into the universe that same thought in energy will make it's way back to you, who knows, maybe in the form of unkind words said to you or about you. That's what we human being call "Karma". Basically our actions have consequences, and the universe is always tuned into us.