"Click traffic" refers to a pay-per-click (PPC) service provided by companies. Banner ads are created to direct traffic, or visitors, to a person's page. The traffic driven to this link is tracked through the amount of clicks on that link. When a person purchases traffic, they purchase a certain amount of clicks to the link contained in the banner ad, which is placed on relevant websites.
This is not purchasing leads. PPC can only guarantee clicks to a link. Since these are real clicks to a link in real time, leads can never be guaranteed, since it is the visitors decision to opt-in for more information or not.