PPC I don’t get the last few steps

I am learning about PPC. I just don’t understand that last steps.
Conversion, Commissions etc.
I decide to promote a product for an affiliate let say Click Bank
I set up an Ad with Adword ,Overture or Adcenter

Some one click the add and it goes to my landing page. He or she wants to buy the product or service
Then What ? Do I actually have to set up a store ?
How do I get my commission let’s say from clickbank?
Do I need to redirect the visitor from my landing page to the actual affiliate web site ?
Sincerely,
Marco

See original post by speedyj