a partnership with another website who pays you for any customers you bring to them
An agreement by the operator of a website A to pay commission to the operator of website B who displays an advert so that visitors are either directed to or make purchases from website A. Affiliate programmes account for the plethora of adverts for certain companies which can be found on so many websites.
A scheme where you are paid for referring customers to another website by including a link to it on your website.