The Constitution was written with the preamble coming in first to explain why they wrote it and stuff.
The articles come next, and they lay out how the government will work (like what powers each branch has, etc.)
The federalists believed that this was enough, but the anti-federalists pressured them into adopting a bill of rights (the first 10 amendments) to ensure that the rights of the people would not be taken away. The amendments are changes to the Constitution and come last. Credit to Brainly user