PPS stands for Pay Per Sale. A PPS offer typically pays more per individual sale/signup, but it often has a lower associated conversion rate than its PPL (pay-per-lead) counterpart. This is because PPS offers require the user to enter their credit card information to classify as a sale. In most cases, assuming the user enters their credit card information, the affiliate will still earn the PPS commission even on trials. To better understand this check the options available on the end of the affiliate program you are working with. Some have special deals on holidays and you are the one, who has to take advantage of this.