Hi,

You mean technichally how is it done or you mean why does he do it?

The reason why he does it is to gain an advantage over all the oterh affilaites promoting the same thing, to give a better deal and make more money.

Technichally speaking, you can log in to your clickbank account and see the e-mail of the people who have purchased through your ilnk, and send the bonus to them that way.

To come up with a bonus you should think of something tat could complement the main product you are promoting. Is there something lacking that you can provide? Don't offer old PLR products in an unrelated market for example.

If you can provide real value in your bonus you will make more money.