I think PPL is pay per lean and PPC is pay per click! But PPC is mostly using for Internet marketing which gives instant traffic!
pay per lead means you get paid when a specific action has been completed such as submitting an email or an application form. pay per click means you get paid when someone has clicked on an ad or banner.
Ye PPC is per click, so everytime some clicks a link to you, you pay. PPL is when someone completes an action on your site. PPL programs are easier to manage because you can see the results of all your traffic.