What are the three branches of the national government?

The three branches of the national government are the legislative, the executive, and the judicial.

The legislative branch is the Congress.  In general, their job is to make the laws for the country.

The executive branch is headed by the President.  It also includes all the government workers like the FBI, the CIA, the IRS, the Park Service, etc.  Their job is to carry out (execute) the laws that are made by the Congress.

The judicial branch is headed by the Supreme Court.  It also includes other federal courts.  Its job is to interpret the laws made by Congress and to interpret the Constitution.

In these ways, there are three branches that all have different jobs to do.  This is called Separation of Powers.