The term affiliate has two general definitions in business contexts:
In corporate law and taxes, an affiliate is a company that is related to another company, usually by being in the position of a member or a subordinate role. Two companies may be affiliated if one company has control over the other or if both are controlled by a third company.
One corporation can be affiliated with another corporation by shareholdings, by holding a minority interest, or one corporation might be a subsidiary of another.
In online retailing, one company may affiliate with another to sell products or services. The seller has a website, on which affiliates may sell products. The seller has control over the site and pays a commission to affiliates. This relationship is sometimes called "affiliate marketing."