what does a function do in js code example

Example 1: function javascript

var x = myFunction(4, 3);     // Function is called, return value will end up in x

function myFunction(a, b) {
    return a * b;             // Function returns the product of a and b
}

Example 2: function js

function toCelsius(fahrenheit) {
  return (5/9) * (fahrenheit-32);
}