It is emphatically the province and duty of the Judicial Department to say what the law is. How does this excerpt summarize the case?

Chief Justice John Marshall stated last 1803 in the case of Marbury v. Madison that "It is emphatically the province and duty of the judicial department to say what the law is. Those who apply the rule to particular cases, must of necessity expound and interpret that rule. If two laws conflict with each other, the courts must decide on the operation of each."

It implies that the judicial department applies the law and the understanding and interpretation therein would still be based on the designated person. If soever, the interpreter or representative in the judicial department would make any conflict with the intent, process, actual application of the law (the two representation of law), the courts would be the end to finalize the decision.