Hi so,
this means that treaties are made under its authority. they take priority over any conflicting state laws. it basically refers to all laws in force that are within a country/feign. this includes statute law+ case-made law. the literal term supreme law of the land refers to the highest, most authorian form of law given in a country. so basically all in all, all treaties made, or shall be made under the authority of the united states shall be the supreme law of land, and the judges in every state shall be bound thereby.
i’m not good at explaining but hopefully u can piece this together .