Can anyone tell me about Event Handling...

Question

I am stuck in CallBack method and event handling.... The problem in event handling is that I want to know say if you're adding a comment on a website and you are typing in it then where does the event occur and who handles the event website or the OS and does the website also have event handlers ??

second I want to know how does a callback method works..
with examples..

Answer 1

I'm a beginner so please answer as simple as you can..