What are the reasons to create the legislative, judical court and executive court?

Federal courts hear cases involving the constitutionality of a law, cases involving the laws and treaties of the U.S. ambassadors and public ministers, disputes between two or more states, admiralty law, also known as maritime law, and bankruptcy cases. The federal judiciary operates separately from the executive and legislative branches, but often works with them as the Constitution requires. Federal laws are passed by Congress and signed by the President. The judicial branch decides the constitutionality of federal laws and resolves other disputes about federal laws. However, judges depend on our government’s executive branch to enforce court decisions.
Courts decide what really happened and what should be done about it. They decide whether a person committed a crime and what the punishment should be. They also provide a peaceful way to decide private disputes that people can’t resolve themselves. Depending on the dispute or crime, some cases end up in the federal courts and some end up in state courts. Learn more about the different types of federal courts.

The answer would be political systems .