Well, I do understand what mathematical theorem means, and I also know what differential equation is but I don't really get why sometimes certain things are called "equations" instead of "law" (Maxwell's equations, nobody calls it Maxwell's laws) and conversely some equations are called laws (Newton's second law, Hook's law, well people do refer to them as equations because they are, but officially they are called laws). Uncertainty principle, Pauli exclusion principle, Fermat principle, why not rule, why Hund's rule is a rule? Noether's theorem, why theorem, because she was a mathematician? LOL. Liouville's theorem (in Hamiltonian mechanics), why theorem again? Law of large numbers, now that's pure mathematics why call it a law when it has a proof? And etc.