1.) All debts contracted and engagements entered into, before the adoption of this Constitution, shall be as valid against the United States under this Constitution, as under the Confederation.
2.) This Constitution, and the laws of the United States which shall be made in pursuance thereof; and all treaties made, or which shall be made, under the authority of the United States, shall be the supreme law of the land; and the judges in every state shall be bound thereby, anything in the Constitution or laws of any State to the contrary notwithstanding.
3.) The Senators and Representatives before mentioned, and the members of the several state legislatures, and all executive and judicial officers, both of the United States and of the several states, shall be bound by oath or affirmation, to support this Constitution; but no religious test shall ever be required as a qualification to any office or public trust under the United States.
What does it mean?
1.) Clause 1 declares that all debts incurred under the Articles of Confederation (the laws of the United States before the Constitution) would be honored under the new Constitution.
2.) Clause 2 establishes the Constitution as the "supreme law of the land" and all treaties must comply with the Constitution.
3.) Clause 3 requires all members of Congress to swear to uphold the Constitution. Clause 3 also prohibits religious tests for public office in federal and state governments.