What does form a perfect union mean in the constitution?

this is referring to the connections between the states. the Framers wanted to form a country where the states worked together. the previous government, the Articles of Confederation, gave all the states far to much power. new york and New Jersey almost went to war with each other over the selling price of Apples. the Framers wanted to stop things like this from happening so they made a government where the states and the central government had more balanced powers. look up "Federalism" for more on that.