Two main concepts are used in PPC:

• CPA (cost-per-acquisition): With this model, the affiliate gets paid each time the seller or retailer acquires a lead, which is when an affiliate link takes the customer to the merchant’s online store and they take an action, such as subscribing to an email list or filling out a “Contact Us” form.
• EPC (earnings-per-click): This is the measure of the average earnings per 100 clicks for all affiliates in a retailer’s affiliate program.