What is a call back funciotn code example

Example 1: callback function

function greeting(name) {
  alert('Hello ' + name);
}

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

processUserInput(greeting);

Example 2: callback function

const ironMan = withGloves(withBoots(withArmor(withHelmet(TonyStark))));