A doubt about Closures

MDN Learn
#1

Hi everyone, I was learning closures in JS here on MDN, so I saw an example that I have doubts:

var getCode = (function () {
  var secureCode = "0]Eal(eh&2"; //  A code we don't want external persons be able to change

  return function () {
    return secureCode;
  };
})();

getCode(); // Returns secureCode

I understood the use of IIFE and how it returned the code… my question is:
what would be the difference if I don’t use closure and just return secureCode? Would people be able to change the variable without closure? If so, how?

Thanks in advance!