The rule of law means that no one is above the law, that the law of a land should be applied to everyone, that we all have to abide by the law, and that no one can be above the law, not even, let's say, the president of the United States.
Society would be insane without the rule of law. Nobody would abide by the law, people would be getting murdered, nobody would have any respect for anyone, things would be getting stolen, etc.