what is the index parameter in a foreach code example

Example 1: foreach in javascript

///Simple One
var a = ["a", "b", "c"];
a.forEach(function(entry) {
    console.log(entry);
});


///Function  concept

var fruits = ["apple", "orange", "cherry"];
fruits.forEach(myFunction);

function myFunction(item, index) {
  document.getElementById("demo").innerHTML += index + ":" + item + "<br>";
}

Example 2: javascript foreach call specific value in array

run.addEventListener("click", function () {
    people.forEach((element) => console.log(element.firstname));
  }); // select a specific string in array