When we pass a function expression (an anonymous function) or the pointer (variable name, declared function name) to a function as an argument, the passed function is called a callback. Since the receiving function will execute, or call that function at a later time; that is, it will call it back, it is called a callback.
So here is a more focused example:
function myDisplayer(number) {
console.log("Displaying number : "+ number);
}
function myCalculator(number, myCallback) {
myCallback(number);
}
myCalculator(100, myDisplayer); // displays the number 100
Using a callback, you could call the calculator function (myCalculator) with a callback, and let the calculator function run the callback after the calculation is finished. In the example above, myDisplayer is the name of a function. It is passed to* myCalculator()* as an argument. When you pass a function as an argument, remember not to use parenthesis.
The reason why I posted this is : I am a little unsure of call back functions because I don’t use them that often (even though they seem very useful). The explanation in our curriculum is again not atomic (so I am removing extraneous details). The source code above is aimed at demonstrating just a call back function in a focused way without any flourishes.