PPI stands for pay per install whereas PPD stands for pay per download.
Pay per install is where when you go to download a software along with it a toolbar comes or an application.PPI pays less than PPD yet it is a lot more typical you will acquire a sale as a result of the fact that not everyone manages to finish the deals given by a PPD. PPI just works with software program nonetheless, it has a general rate around 1$ for US installs and also 0.50 for various other countries. Whereas in PPD depending on the country as well as the offer the individual finishes you can make 25$+ on a single sale. An example of PPD is AjaxFiles and for PPI isPerInstallCash.
The image below shows the payout rate an affiliate network (CashMyLinks) pays for every transfer done with their software. The amount is dependent on the geographic location obviously. But the bottomline is, affiliating offer earns cash.