Article I of the Constitution of the United States establishes the powers and limits of Congress. Congress is the legislative branch of the government. It also creates the two chambers of the legislature: the Senate and the House of Representatives.
Article II is the one that establishes the executive branch of the government. The executive branch in the U. S. includes the President. It is also the branch that has the responsibility and authority for the administration of the state.
Article III establishes the judicial branch of the federal government. This includes the Supreme Court of the United States and the lower courts created by Congress.