An affiliate ID is a unique identifier assigned to an affiliate, or publisher, in an affiliate marketing program. This ID is used to identify the affiliate who is promoting a merchant's products in order to receive a commission. Affiliate IDs are typically included in the link that the affiliate shares on their website or blog, or in an email sent to their audience. For example, a fitness blogger might partner with a fitness equipment company to promote their products in exchange for commissions. The company could assign the blogger an affiliate ID that would be included in the link that the blogger shares with their audience. If a customer clicks on the link and makes a purchase, the affiliate ID would then be used to track the sale and attribute it back to the blogger, allowing them to receive their commission for the sale.