The Constitution of the United States has seven main parts. These parts are called articles. The articles set out the basic three-branch structure of the US government and the relationship between the states and the national government. The articles then go on to say how the Constitution can be amended and how it is to be ratified.
Articles I, II, and III set out the ways in which the three branches of the federal government will work. Article I deals with the legislative, Article II with the executive, and Article III with the judicial. Article IV deals with the states and their relationships with one another and with the national government. Article V sets out a process for amending the Constitution. Article VI establishes that the federal government has supremacy over the state governments in any issues where both may legislate. Finally, Article VII lays out the requirements for ratifying the Constitution.