Product link is the URL to which the website visitor is taken from the publisher website to the advertiser website. Affiliate product link includes the affiliate id which is essential to track the source of the visitor. When the visitor from your website clicks on your product link and makes a purchase, you can earn commissions based on the quantity of sales. When you sign up with an affiliate marketing program, you will be provided with a specific link to the merchant website. You should always use the product link provided to you so that you are credited for the sales made by your website visitor. It is the responsibility of the affiliate to ensure that the right product link is placed on the website.