A lead is when you direct a user to sign up for something somewhere. A click is when a user clicks a banner or text link. Pay per lead means that you get a commission when the user clicks, and then does something (like signs up to a trial or 'free' membership). Pay per click, is exactly that - you get paid everytime somebody clicks. http://en.wikipedia.org/wiki/Pay_per_Lead http://en.wikipedia.org/wiki/Pay_per_click