what is the difference between normal function and self invoking function - JS

Question

I'm learning Javascript

What is difference between these two codes as they both return the same output

var getcode = function(){
    var apicode = '0]Eal(eh&2';
    return apicode;
}
getcode();

var getCode = (function() {
  var apiCode = '0]Eal(eh&2';   

  return function() {
    return apiCode;
  };
})();

getCode();