How to explain callbacks in plain english? How are they different from calling one function from another function?

Question

How to explain callbacks in plain English? How are they different from calling one function from another function taking some context from the calling function? How can thei

Answer 1

Always better to start with an example :).

Let's assume you have two modules A and B.

You want module A to be notified when some event/condition occurs in module B. However, module B has no idea about your module A. All it knows is an address to a particular function (of module A) through a function pointer that is provided to it by module A.

So all B has to do now, is "callback" into module A when a particular event/condition occurs by using the function pointer. A can do further processing inside the callback function.

*) A clear advantage here is that you are abstracting out everything about module A from module B. Module B does not have to care who/what module A is.