Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, Records and Proceedings shall be proved, and the Effect thereof.
Officials acts, records, or judgements of one state will be honored in every other state. Congress may pass laws saying what kinds of proof must be offered. (This means, for example, that a marriage or a will or a court decision that is legal in one state will be recognized by every state.)