Assignment with a Returned Value - callback?

I am curious what is meant by a “callback function”. This excercise has a function with a return:

function processArg(num) {
  return (num + 3) / 5;

Is this a callback because it has the return?

It’s just a name for a function passed as an argument to another function that triggers some kind of action. The main function gets called, with another function passed as an argument to it. At some point after the outer function is called, the inner function is triggered.

Edit: Answer to your question is no

Edit: example. addEventListener is a function that takes a function as an argument. When the click happens, that inner function triggers.

button.addEventListener('click', function () {
  return "I got clicked";

No, a callback is when you have a function as parameter of an other function or of a method
For example used like this processArg is a callback