Hi. Nice article, but I have a slight quibble with your definition of a callback. The important part of a callback is that it is called by some other function, not that it is called at the end of the other function.

Wikipedia says this:

In computer programming, a callback, also known as a “call-after”[1] function, is any executable code that is passed as an argument to other code; that other code is expected to call back (execute) the argument at a given time.

https://en.wikipedia.org/wiki/Callback_(computer_programming)