" what sorts of things are provable in math "
Can one apprise us, the ordinary persons, what are those things that are provable in math and those that not provable, please?
Regards
Well, mathematics has a set of basic assumptions, which we call the axioms. The modern set of axioms deals with the properties of sets. All of the rest of math is defined in terms of sets, including numbers, functions, vectors, geometry, etc. EVERYTHING is ultimately a set in modern mathematics.
So, everything in math is proven from those axioms and the rules of deduction (carried over from logic). A proof is a sequence of statements, where each statement is either an axiom or follows from two previous statements by a rule of deduction. Something is provable if there is a proof for it and not provable if there is not.
What Godel showed is how to investigate the notion of proof algebraically, finding common properties of all proofs and thereby showing that there are statements that are independent: that they cannot be proved, NOR can they be proved false.
Furthermore, he did this in a very general context that showed whenever the axioms are enough to talk about numbers, such independent statements can be found. Simply adding in more axioms doesn't fix this issue.
The specific questions that cannot be proved nor disproved tend to be technical. This is one reason why such statements won't impact the models used in science: the technicalities are such that experimental observations will never be able to resolve those issues.
One that is very commonly mentioned is the Continuum Hypothesis. This deals with the cardinalities of subsets of the set of real numbers (decimal numbers) and asks if there is some infinite subset that cannot be put into correspondence with either the set of natural numbers (counting numbers) nor the set of real numbers. The actual CH says that there are no such subsets.
It turns out that this cannot be proved from the standard axioms. Nor can it be shown from those axioms that there *is* a set with those properties. So CH is independent of the standard axioms. it can neither be proved nor disproved.