A callback is a function that is executed through a pointer where the function being pointed to contains application specific code. Callbacks are normally passed into a function and provides the ...

The callback functions are invoked in response to events. The createServer callback handles a client request event and returns a response. The listen callback handles the listening event.

However, in C you have to define a function by name and pass a pointer — not a huge problem, but it can get messy if you have a lot of callback functions that you use only one time.