what does it mean callback in javascript code example

Example 1: javascript callback

/*
A callback function is a function passed into another function
as an argument, which is then invoked inside the outer function
to complete some kind of routine or action. 
*/
function greeting(name) {
  alert('Hello ' + name);
}

function processUserInput(callback) {
  var name = prompt('Please enter your name.');
  callback(name);
}

processUserInput(greeting);
// The above example is a synchronous callback, as it is executed immediately.

Example 2: callback function js

function myDisplayer(some) {  document.getElementById("demo").innerHTML 
  = some;}function myCalculator(num1, num2, myCallback) {  
  let sum = num1 + num2;  
  myCallback(sum);}myCalculator(5, 5, myDisplayer);