What is judicial review? explain its orgins and significance?

Judicial review is the power of the judiciary branch to rule on whether laws are constitutional. This power was not given to the court in the Constitution, but rather came about as the result of the ruling in the case Marbury v. Madison. It is significant because it is one of the checks that the judiciary branch has to balance the other two branches of government. It's also what makes the judiciary important in the first place. Without judiciary review, the courts would mean nothing.