What is the function of the articles, or main body, of the constitution?

Together, the articles of the constitution work to establish the branches of the federal government and describe what powers they have. Article 1 gives Congress its powers and limits. Congress is the branch of the government who can make laws for the country 
kids.laws.com/articles-of-the-constitution

To have a bunch of countries to team up, and communicate not let the communist break them apart and take over the world